A pump for circulating water includes an upper housing 10 formed with an inlet 11 and an outlet 12 of fluid; a lower housing 20 arranged in a lower side of the upper housing 10, having a space formed therein; an inner housing 30 having an edge part interposed between the upper housing 10 and the lower housing 20, and an impeller receiving space 31 formed in a middle part; an impeller 50 received inside the upper housing 10 and in the impeller receiving space 31 to be rotatably installed; a rotor 60 installed inside an outer circumference of the impeller 50; a spring 65 installed between a lower surface of the impeller and the inner housing; and a stator 70 installed inside the lower housing 20.