To provide a water pump capable of preventing a coolant from intruding into a rolling bearing even if a hole for discharging the coolant to the outside is closed or a large amount of coolant leaks from a mechanical seal.

The seal 55 of the rolling bearing 5 for rotatably supporting a rotating member 2, having a shaft part 21 on which an impeller 1 is mounted and a pulley part 22 around which a belt 3 is wrapped which are formed integrally with each other, on a body 4 is fixed to an inner ring 51 on its inner peripheral part by installing the rotating member 2 on an outer ring 52 and fixing the inner ring 51 to the body 4, and a lip part 55a formed on the outer peripheral part is formed so as to be come into slidable contact with the outer ring 52. Thus, even if the coolant is accumulated near the inner ring 51, such a state that the lip part 55a is immersed in the coolant does not occur, and the entry of the coolant into the rolling bearing 5 can be prevented.