A washing machine comprising: a washing tub; a water supply valve which is opened and closed to supply tap water into the washing tub; a bathwater pump which is driven to supply bathwater from a supply external to the washing machine into the washing tub; a water circulation passage (42, 43, 44, 45, 15, 55, 25, 57, 26, 58, 59) having opposite ends connected to the washing tub; a circulation pump provided in the water circulation passage for pumping water out of the washing tub through one of the opposite ends of the water circulation passage and supplying the pumped water back into the washing tub through the other end of the water circulation passage; a cleaning air generator which generates cleaning air; and a gas-liquid mixer provided in the water circulation passage for mixing the cleaning air generated by the cleaning air generator with water flowing through the water circulation passage, characterized by comprising: control section (120, P4) for the bathwater pump for supplying the bathwater into the washing tub by driving the bathwater pump in a rinsing step; and bathwater cleaning controlling means (120, P15, P17, P18) for purifying the bathwater by driving the circulation pump to circulate the bathwater retained in the washing tub through the circulation passage and by actuating the cleaning air generator to mix the cleaning air into the circulating bathwater through the circulation passage in response to supply of the bathwater into the washing tub by the control section for the bathwater pump in the rinsing step. a washing tub; a water supply valve which is opened and closed to supply tap water into the washing tub; a bathwater pump which is driven to supply bathwater from a supply external to the washing machine into the washing tub; a water circulation passage (42, 43, 44, 45, 15, 55, 25, 57, 26, 58, 59) having opposite ends connected to the washing tub; a circulation pump provided in the water circulation passage for pumping water out of the washing tub through one of the opposite ends of the water circulation passage and supplying the pumped water back into the washing tub through the other end of the water circulation passage; a cleaning air generator which generates cleaning air; and a gas-liquid mixer provided in the water circulation passage for mixing the cleaning air generated by the cleaning air generator with water flowing through the water circulation passage, characterized by comprising: control section (120, P4) for the bathwater pump for supplying the bathwater into the washing tub by driving the bathwater pump in a rinsing step; and bathwater cleaning controlling means (120, P15, P17, P18) for purifying the bathwater by driving the circulation pump to circulate the bathwater retained in the washing tub through the circulation passage and by actuating the cleaning air generator to mix the cleaning air into the circulating bathwater through the circulation passage in response to supply of the bathwater into the washing tub by the control section for the bathwater pump in the rinsing step. control section (120, P4) for the bathwater pump for supplying the bathwater into the washing tub by driving the bathwater pump in a rinsing step; and bathwater cleaning controlling means (120, P15, P17, P18) for purifying the bathwater by driving the circulation pump to circulate the bathwater retained in the washing tub through the circulation passage and by actuating the cleaning air generator to mix the cleaning air into the circulating bathwater through the circulation passage in response to supply of the bathwater into the washing tub by the control section for the bathwater pump in the rinsing step.