a water pump of clutch type 1 includes a pump housing 40 a pump cover not shown a pulley 10 a hub 80 a shaft 20 and a coil 110 the pump housing 40 has a disk shape and is provided with a penetration hole formed at a middle portion thereof coupling means for coupling the pump housing 40 with the pump cover are disposed at an external circumferential portion of the pump housing 40 generally a bolt not shown is used as the coupling means the shaft 20 is disposed in the penetration hole and an impeller 30 is fixed to one end of the shaft 20 a bearing for smoothly rotating the shaft 20 is disposed between the shaft 20 and the penetration hole the pump cover is coupled with the pump housing 40 so as to form a chamber not shown therebetween in which coolant is pressurized the impeller 30 is disposed in the chamber in addition the chamber is connected to an inlet not shown so as to receive the coolant circulating a cooling circuit not shown and is connected to an outlet not shown such that the pressurized coolant is supplied to the cooling circuit the impeller 30 rotates together with the shaft 20 and pressurizes the coolant flowing in the chamber the pump housing 40 the pump cover and the impeller 30 according to an exemplary embodiment of the present invention are similar to those according to conventional arts and are well known to a person of an ordinary skill in the art therefore a detailed description thereof will be omitted the pulley 10 has an annular shape.