To provide a self-priming type pump capable of reducing vibration and noise by restraining an interference between a communicating hole to return circulating water and an impeller.

A communicating hole 8 is made in a slender open shape along a position roughly corresponding to an outer peripheral edge of an impeller 12, and an interfering area of a vane 12a of the impeller 12 and the communicating hole 8 is reduced on a self-suction type pump furnished with an impeller casing 3 and a pumping water casing on which an impeller chamber 11 to store the outside driving type impeller 12 is furnished on the impeller casing 3, first and second circulation chambers are furnished on the pumping water casing 4 and the communicating hole 8 to return water to the impeller chamber 11 from the first and second circulation chambers is drilled on a partition plate 6 to divide the impeller casing 3 and the pumping water casing 4.