A method for cleaning and sterilizing an excreta handling device includes: positioning one end and the other end of the suction pipe on the same line; driving the pump to supply the cleaning water to a preset water level in the inner space through the first nozzle part; and maintaining, for a predetermined time, a state in which the cleaning water has been supplied to the preset water level, and then driving the suction part to suck the cleaning water contained in the inner space.