In a mechanical element such as a uniform velocity type universal joint having an inner joint member and one of a plurality of spherical ball elements or an outer joint member and one of the spherical ball elements, the ball rolls and slides on the surface of either or both of the inner and outer joint members thus generating relative harmonic vibrations due to a frictional force generated thereon by the sliding contact between the ball and the joint members. To reduce high-frequency harmonic vibrations, a pair of piezoelectric actuators are installed between a flange of one rotation axle of the (constant) uniform velocity type universal joint and the outer joint member and/or between a mounting bolt head of the universal joint and the outer joint member. The piezoelectric actuators expand and constrict at a phase different from that of an input vibrating force acting upon and between the inner joint member and each spherical ball element or at a frequency different from a rotation frequency of the universal joint.