PURPOSE: To prevent the racing of blades even in the case of water stopping partially in the fluid passage of a pump by providing a vortex chamber partitioning disc with holes or recessed parts for communicating one vortex chamber part with the other vortex chamber part.

CONSTITUTION: In a feed water pump 1, an impeller 3 provided in a vortex chamber 4 is formed of a disc 3a and blades 3b formed at the disc 3a. The disc 3a partitioning one vortex chamber part 4A from the other vortex chamber part 4B is provided with holes 33 for communicating the vortex chamber parts 4A, 4B with each other. Accordingly, even if water stops between the vortex chamber 4 and a discharge opening 9 for some reason, air in the vortex chamber part 4B is removed into the vortex chamber part 4B through the holes 33 to lead water in around the blades 3b. Stable water supply can be thereby performed without generating the racing of the blades 3b.