A driving device including a drive shaft and a first engaging member. The drive shaft rotates around a first axis. The first engaging member is disposed on the first axis to rotate integrally with the drive shaft. The power transmission mechanism includes a second engaging member, a propeller shaft, a piston, and a reduction gear. The second engaging member is disposed on the first axis engageable with/disengageable from the first engaging member. The propeller shaft is rotatable integrally with the second engaging member around the first axis. The piston reciprocates the second engaging member between a first position and a second position along a direction of the first axis. The reduction gear is joined to the other end side of the propeller shaft to decelerate the rotation of the propeller shaft. The reduction gear causes an output shaft joined to an object to rotate around a second axis.