A motor device having a hollow casing in which a mechanism for converting continuous rotational motion of a rotating member into reversible rotational motion to transmit the converted motion to an output shaft. This motor device includes an oscillation member which oscillates around the output shaft. Further, it includes a driving force conversion member which is interposed between the oscillating member and the rotating member, and which converts the continuous rotational motion of the rotating member into reciprocating oscillatory motion of the oscillating member. This driving force conversion member includes a contacting portion which projects toward an inner wall of the hollow casing and which is formed integrally with the driving force conversion member. This contacting portion slides on the inner wall of the hollow casing over the range of displacement of the driving force conversion member, and moreover is formed from a material which is capable of absorbing sound generated by sliding motion. In this manner, it is possible to reduce sound such as vibrational noise and the like caused by sliding motion.