A drain pump that maintains pump performance and reduces noise and vibration accompanying water scooping of a rotary impeller includes a large-diameter blade divided into an inner blade and an outer blade. A radius of an impeller scooping up water is the sum of the lengths of the inner and outer blades in a radial direction. The large-diameter blade is divided at a position where the amount of generated air bubbles is large, and the inner and outer blades are alternately disposed. Accordingly, air bubbles are escaped to a downstream side in a rotational direction, so that the intensity of the collision between the blades and air bubbles is decreased reducing noise caused by the burst of air bubbles and vibration caused by a collision load of the flow of a gas-liquid mixture.