To simplify a structure of a delivery chamber ranging from a delivery port to a self-suction port in a vortex flow chamber of a self-priming centrifugal pump.

This self-priming centrifugal pump is provided with an impeller 18 in which a rotary shaft axis rises, the vortex flow chamber 13 opening a suction port 11 on a lower side and a delivery port 12 on a side and storing the impeller 18, the delivery chamber 14 extended below the vortex flow chamber 13 from the delivery port 12 in the vortex flow chamber 13, the self-suction hole 15 opened on a lower side of the vortex flow chamber 13 to communicate the vortex flow chamber 13 with the delivery chamber 14, and a discharge chamber 5c erected from the delivery chamber 14. One delivery port 12 is provided. The delivery chamber 14 is provided with a curved region 14a on the upstream side swelling so as to expand like a plane to the side and outside of the vortex flow chamber 13 and a lower region 14b on the downstream side positioned below the vortex flow chamber 13. An external wall face 14a extended from the delivery port 12 and curved like a recessed part onto an indoor side is formed on the indoor side of the curved region 14a. An inclined bottom face 14d inclined downward from the curved region 14a toward the lower region 14b is formed across both regions 14a, 14b, and the discharge chamber 5c is positioned above the inclined bottom face 14d of the delivery chamber 14.