PURPOSE: To provide an inexpensive music box unit equipped with strength for preventing a music box mechanism from being damaged even when stress is applied to a rotary transmission shaft.

CONSTITUTION: A music box unit 1 is provided with a metallic drum shaft part 8 to be revolved integrally with a drum 6 inside a music box mechanism 3 and a synthetic resin swinging shaft part 9 provided with a bent part at its intermediate part and flexibility or elasticity while supporting a movable body 2B whose one end 9c is linked to the drum shaft part 8 and other end 9b is operated with the ringing of the music box mechanism. Then, the rotary transmission shaft for transmitting the rotation of the drum 6 to the movable body 8 is composed of the drum shaft part 8 and the swinging shaft part 9.