The main results obtained are as follows: (1)New ultra-smoothness grinding method is useful for finishing the cemented carbide to the ultra-smoothness surface. (2)At the normal feed of 10 micro-meter/rev, the 2D surface roughness becomes below 20nm(Rz). The surface roughness increases steeply and transiently until the normal feed of 30 micro-meter/rev and keeps about 100nm(Rz) over the normal feed of 30 micro-meter/rev. (3)The 3D surface roughness increases with increase of parallel feed. The increase rate is small. Even at fp=50 micro-meter, the 3D surface roughness becomes below 50nm(Rz).(4)The 3D surface roughness of cemented carbide formed using the suitable grinding condition attains about 25nm(Rz) or 2.5nm(Ra).