A self-priming chemical pump which comprises: a pump portion including at least an impeller and a shaft supporting the impeller; a self-priming mechanism portion including a self-priming chamber which is provided in the discharge side of a vortex chamber of the impeller so as to communicate with a discharge opening, and a suction chamber which is provided in the suction side of the vortex chamber of the impeller so as to communicate with a suction opening; a seal wall which is provided in the vicinity of the discharge side of the vortex chamber to form a slight gap along the outer circumference of the impeller; and a circulation hole which is provided in the self-priming chamber so as to be located inside the outer circumference of the impeller.