To provide a water pump for a vehicle in which an operation state and a stopped state thereof are switched by a compact clutch mechanism at a given timing according to a warming-up state of each part of the vehicle such as an internal combustion engine.

The water pump for a vehicle includes a pulley 2 driven and rotated by an externally located power, a driven shaft 5 rotatable independently from the pulley 2, an impeller 7 to which rotation of the driven shaft 5 is transmitted, a wrap spring 3 for contactably pressing an inner circumferential surface 2a of the pulley 2 and for rotating in order to transmit rotation of the pulley 2 to the driven shaft 5 when the wrap spring 3 contacts the inner circumferential surface 2a of the pulley 2, and having a shape being wound around in a circumferential direction of the pulley 2, and a control member 4 for allowing the pulley 2 and the wrap spring 3 to come in contact with each other or to come out of contact from each other and for controlling a contacting state by controlling the radial length of the wrap spring 3.