To provide a superior cutoff effect at low cost by integrally forming a projection preventing a packing part from sticking out by a pump internal pressure and preventing the liquid in a pump from flowing to the outside in a check valve interposed between a water suction port and a easing and composed of a rubber elastic body.

In this self-priming pump 1, a water suction port 3 for sucking fluid to a easing 2 is fastened by a fastening bolt 4 and a check valve 6 is interposed between the easing 2 and the water suction port 3. The check valve 6 is set to a rubber elastic body and integrally formed with a cutoff packing 7 provided in such a state as surrounding its circumference. The cutoff packing 7 is fastened by the fastening bolt inserted in a bolt hole formed in its edge part and a projection 5 is projected from a part 7a decreasing the fastening bearing pressure in fastening. This constitution can prevent the cutoff packing 7 from sticking to the outside in acting the pump internal pressure in the instant of stopping the pump and surely prevent the liquid from leaking therefrom.