The invention provides a drainage pump. Even though the pump is under a low-lift condition, the sound pressure level of the bailing sound generated by a pump rotor can be reduced and the miniature of the drainage pump can be realized. The pump rotor (12) is configured by including a plurality of protruding sheets (20ai)(i=1-72) of a stirrer, and a conical support body (12A) having a shaft part (12B) inserting into an intake port (10a) at the lower end and integrated with the lower ends of the protruding sheets (20ai), and a clearance (CL) greater than 1mm and less than 2mm is formed between the outer peripheral surface of the support body (12A) of the pump rotor (12) and the inner peripheral surface of the side wall of a casing (10).
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