diff --git a/include/mcl/bn.h b/include/mcl/bn.h
index b910025..6e5d1ff 100644
--- a/include/mcl/bn.h
+++ b/include/mcl/bn.h
@@ -279,20 +279,22 @@ MCLBN_DLL_API int mclBnFr_isValid(const mclBnFr *x);
 MCLBN_DLL_API int mclBnFr_isEqual(const mclBnFr *x, const mclBnFr *y);
 MCLBN_DLL_API int mclBnFr_isZero(const mclBnFr *x);
 MCLBN_DLL_API int mclBnFr_isOne(const mclBnFr *x);
+MCLBN_DLL_API int mclBnFr_isOdd(const mclBnFr *x);
+// return 1 if half <= x < r, where half = (r + 1) / 2 else 0
+MCLBN_DLL_API int mclBnFr_isNegative(const mclBnFr *x);
 
 MCLBN_DLL_API int mclBnFp_isValid(const mclBnFp *x);
 MCLBN_DLL_API int mclBnFp_isEqual(const mclBnFp *x, const mclBnFp *y);
 MCLBN_DLL_API int mclBnFp_isZero(const mclBnFp *x);
 MCLBN_DLL_API int mclBnFp_isOne(const mclBnFp *x);
+MCLBN_DLL_API int mclBnFp_isOdd(const mclBnFp *x);
+// return 1 if half <= x < p, where half = (p + 1) / 2 else 0
+MCLBN_DLL_API int mclBnFp_isNegative(const mclBnFp *x);
 
 MCLBN_DLL_API int mclBnFp2_isEqual(const mclBnFp2 *x, const mclBnFp2 *y);
 MCLBN_DLL_API int mclBnFp2_isZero(const mclBnFp2 *x);
 MCLBN_DLL_API int mclBnFp2_isOne(const mclBnFp2 *x);
 
-// return 1 if half <= x < r, where half = (r + 1) / 2 else 0
-MCLBN_DLL_API int mclBnFr_isNegative(const mclBnFr *x);
-// return 1 if half <= x < p, where half = (p + 1) / 2 else 0
-MCLBN_DLL_API int mclBnFp_isNegative(const mclBnFp *x);
 
 #ifndef MCL_DONT_USE_CSRPNG
 // return 0 if success
diff --git a/include/mcl/impl/bn_c_impl.hpp b/include/mcl/impl/bn_c_impl.hpp
index f9c3f13..51112a7 100644
--- a/include/mcl/impl/bn_c_impl.hpp
+++ b/include/mcl/impl/bn_c_impl.hpp
@@ -175,6 +175,10 @@ int mclBnFr_isOne(const mclBnFr *x)
 {
 	return cast(x)->isOne();
 }
+int mclBnFr_isOdd(const mclBnFr *x)
+{
+	return cast(x)->isOdd();
+}
 int mclBnFr_isNegative(const mclBnFr *x)
 {
 	return cast(x)->isNegative();
@@ -731,6 +735,10 @@ int mclBnFp_isOne(const mclBnFp *x)
 {
 	return cast(x)->isOne();
 }
+int mclBnFp_isOdd(const mclBnFp *x)
+{
+	return cast(x)->isOdd();
+}
 int mclBnFp_isNegative(const mclBnFp *x)
 {
 	return cast(x)->isNegative();
diff --git a/test/bn_c_test.hpp b/test/bn_c_test.hpp
index 45095b7..9c1818b 100644
--- a/test/bn_c_test.hpp
+++ b/test/bn_c_test.hpp
@@ -351,6 +351,27 @@ CYBOZU_TEST_AUTO(Fp_isNegative)
 	CYBOZU_TEST_ASSERT(mclBnFp_isNegative(&a));
 }
 
+CYBOZU_TEST_AUTO(Fr_isOdd)
+{
+	mclBnFr x, one;
+	mclBnFr_clear(&x);
+	mclBnFr_setInt(&one, 1);
+	for (size_t i = 0; i < 100; i++) {
+		CYBOZU_TEST_EQUAL(mclBnFr_isOdd(&x), i & 1);
+		mclBnFr_add(&x, &x, &one);
+	}
+}
+
+CYBOZU_TEST_AUTO(Fp_isOdd)
+{
+	mclBnFp x, one;
+	mclBnFp_clear(&x);
+	mclBnFp_setInt(&one, 1);
+	for (size_t i = 0; i < 100; i++) {
+		CYBOZU_TEST_EQUAL(mclBnFp_isOdd(&x), i & 1);
+		mclBnFp_add(&x, &x, &one);
+	}
+}
 
 CYBOZU_TEST_AUTO(pairing)
 {