A rotary shaft and a seal mechanism are provided. The rotary shaft extends into outside air outside a case via a shaft hole provided in the case of a drive system. The seal mechanism prevents entry of foreign matter from the outside air into the shaft hole. The case includes a canopy portion and a recessed portion. The recessed portion is recessed coaxially with the canopy portion from an end face of the canopy portion in the direction of the axis. The seal mechanism includes a deflector and a seal member. The deflector is fixed to the rotary shaft in a liquid-tight manner, and extends into the recessed portion. The seal member is an elastic body. The seal member is fixed in the shaft hole in a liquid-tight manner, and is in sliding contact in a liquid-tight manner with the rotary shaft and the deflector.