In a motion conversion mechanism for converting mechanical expansion and compression of a material, such as a piezo electric element, to the motion of the other material, provided are moving member arranged to be movable in accordance with the motion of the material along a predetermined direction, transmitting member for transmitting the movement of the moving member toward the other material along the predetermined direction, and regulating member for regulating the transmitting operation of the transmitting member so as not to be skewed from the predetermined direction. Thus, the transmitting operation of is accurately executed.