diff --git a/include/pocketpy/interpreter/modules.h b/include/pocketpy/interpreter/modules.h
index f3871419..a74f56ab 100644
--- a/include/pocketpy/interpreter/modules.h
+++ b/include/pocketpy/interpreter/modules.h
@@ -5,3 +5,4 @@ void pk__add_module_os();
 void pk__add_module_math();
 void pk__add_module_dis();
 void pk__add_module_random();
+void pk__add_module_json();
diff --git a/include/pocketpy/pocketpy.h b/include/pocketpy/pocketpy.h
index 739b476c..5e139a5f 100644
--- a/include/pocketpy/pocketpy.h
+++ b/include/pocketpy/pocketpy.h
@@ -454,6 +454,8 @@ bool py_str(py_Ref val) PY_RAISE;
 bool py_repr(py_Ref val) PY_RAISE;
 /// Python equivalent to `len(val)`.
 bool py_len(py_Ref val) PY_RAISE;
+/// Python equivalent to `json.dumps(val)`.
+bool py_json(py_Ref val) PY_RAISE;
 
 /************* Unchecked Functions *************/
 
diff --git a/src/interpreter/vm.c b/src/interpreter/vm.c
index bcdabc96..7bb420db 100644
--- a/src/interpreter/vm.c
+++ b/src/interpreter/vm.c
@@ -197,6 +197,7 @@ void VM__ctor(VM* self) {
     pk__add_module_math();
     pk__add_module_dis();
     pk__add_module_random();
+    pk__add_module_json();
 
     // add python builtins
     do {
diff --git a/src/modules/json.c b/src/modules/json.c
new file mode 100644
index 00000000..5a5ca0bf
--- /dev/null
+++ b/src/modules/json.c
@@ -0,0 +1,111 @@
+#include "pocketpy/pocketpy.h"
+
+#include "pocketpy/common/utils.h"
+#include "pocketpy/objects/object.h"
+#include "pocketpy/common/sstream.h"
+#include "pocketpy/interpreter/vm.h"
+#include <math.h>
+
+static bool json_loads(int argc, py_Ref argv) {
+    PY_CHECK_ARGC(1);
+    PY_CHECK_ARG_TYPE(0, tp_str);
+    const char* source = py_tostr(argv);
+    py_TmpRef mod = py_getmodule("json");
+    return py_exec(source, "<json>", EVAL_MODE, mod);
+}
+
+static bool json_dumps(int argc, py_Ref argv) {
+    PY_CHECK_ARGC(1);
+    return py_json(argv);
+}
+
+void pk__add_module_json() {
+    py_Ref mod = py_newmodule("json");
+
+    py_setdict(mod, py_name("null"), py_None);
+    py_setdict(mod, py_name("true"), py_True);
+    py_setdict(mod, py_name("false"), py_False);
+
+    py_bindfunc(mod, "loads", json_loads);
+    py_bindfunc(mod, "dumps", json_dumps);
+}
+
+static bool json__write_object(c11_sbuf* buf, py_TValue* obj);
+
+static bool json__write_array(c11_sbuf* buf, py_TValue* arr, int length) {
+    c11_sbuf__write_char(buf, '[');
+    for(int i = 0; i < length; i++) {
+        if(i != 0) c11_sbuf__write_cstr(buf, ", ");
+        bool ok = json__write_object(buf, arr + i);
+        if(!ok) return false;
+    }
+    c11_sbuf__write_char(buf, ']');
+    return true;
+}
+
+typedef struct {
+    c11_sbuf* buf;
+    bool first;
+} json__write_dict_kv_ctx;
+
+static bool json__write_dict_kv(py_Ref k, py_Ref v, void* ctx_) {
+    json__write_dict_kv_ctx* ctx = ctx_;
+    if(!ctx->first) c11_sbuf__write_cstr(ctx->buf, ", ");
+    ctx->first = false;
+    if(!py_isstr(k)) return TypeError("keys must be strings");
+    c11_sbuf__write_quoted(ctx->buf, py_tosv(k), '"');
+    c11_sbuf__write_char(ctx->buf, ':');
+    return json__write_object(ctx->buf, v);
+}
+
+static bool json__write_object(c11_sbuf* buf, py_TValue* obj) {
+    switch(obj->type) {
+        case tp_NoneType: c11_sbuf__write_cstr(buf, "null"); return true;
+        case tp_int: c11_sbuf__write_int(buf, obj->_i64); return true;
+        case tp_float: {
+            if(isnan(obj->_f64)) {
+                c11_sbuf__write_cstr(buf, "NaN");
+            } else if(isinf(obj->_f64)) {
+                c11_sbuf__write_cstr(buf, obj->_f64 < 0 ? "-Infinity" : "Infinity");
+            } else {
+                c11_sbuf__write_f64(buf, obj->_f64, -1);
+            }
+            return true;
+        }
+        case tp_bool: {
+            c11_sbuf__write_cstr(buf, py_tobool(obj) ? "true" : "false");
+            return true;
+        }
+        case tp_str: {
+            c11_sbuf__write_quoted(buf, py_tosv(obj), '"');
+            return true;
+        }
+        case tp_list: {
+            return json__write_array(buf, py_list_data(obj), py_list_len(obj));
+        }
+        case tp_tuple: {
+            return json__write_array(buf, py_tuple_data(obj), py_tuple_len(obj));
+        }
+        case tp_dict: {
+            c11_sbuf__write_char(buf, '{');
+            json__write_dict_kv_ctx ctx = {.buf = buf, .first = true};
+            bool ok = py_dict_apply(obj, json__write_dict_kv, &ctx);
+            if(!ok) return false;
+            c11_sbuf__write_char(buf, '}');
+            return true;
+        }
+        default: return TypeError("'%t' object is not JSON serializable", obj->type);
+    }
+}
+
+bool py_json(py_Ref val) {
+    c11_sbuf buf;
+    c11_sbuf__ctor(&buf);
+    bool ok = json__write_object(&buf, val);
+    if(!ok){
+        c11_sbuf__dtor(&buf);
+        return false;
+    }
+    c11_sbuf__py_submit(&buf, py_retval());
+    return true;
+}
\ No newline at end of file
diff --git a/src/modules/pkpy.c b/src/modules/pkpy.c
index 96dab19f..0c92366c 100644
--- a/src/modules/pkpy.c
+++ b/src/modules/pkpy.c
@@ -5,7 +5,7 @@
 #include "pocketpy/common/sstream.h"
 #include "pocketpy/interpreter/vm.h"
 
-static bool _py_pkpy__next(int argc, py_Ref argv) {
+static bool pkpy_next(int argc, py_Ref argv) {
     PY_CHECK_ARGC(1);
     int res = py_next(argv);
     if(res == -1) return false;
@@ -17,5 +17,5 @@ static bool _py_pkpy__next(int argc, py_Ref argv) {
 void pk__add_module_pkpy() {
     py_Ref mod = py_newmodule("pkpy");
 
-    py_bindfunc(mod, "next", _py_pkpy__next);
+    py_bindfunc(mod, "next", pkpy_next);
 }
\ No newline at end of file
diff --git a/tests/80_json.py b/tests/80_json.py
index 865abf07..3b5f499f 100644
--- a/tests/80_json.py
+++ b/tests/80_json.py
@@ -14,11 +14,7 @@ a = {
     'h': False
 }
 
-try:
-    import cjson as json
-    print('[INFO] cjson is used')
-except ImportError:
-    import json
+import json
 
 assert json.loads("1") == 1
 assert json.loads('"1"') == "1"
@@ -29,7 +25,7 @@ assert json.loads("true") == True
 assert json.loads("false") == False
 assert json.loads("{}") == {}
 
-assert json.loads(b"false") == False
+# assert json.loads(b"false") == False
 
 _j = json.dumps(a)
 _a = json.loads(_j)