PURPOSE: To provide a water-saving automatic washing device capable of being installed with no special piping work, miniaturize a bathroom unit provided separately from a main body unit, and provide no hindrance during bathing by combining it with a bath water boiler, and decomposing and removing stains with a detergent.

CONSTITUTION: A main body unit 4 is installed outside a bathroom, and a detergent tank 5 and a detergent spray pump 6 are incorporated in it. A drain valve switch 8 opening or closing a drain valve 3 is incorporated in the bathroom unit 7 fitted on the edge of a bathtub 1. The main body unit 4 and the bathroom unit 7 are separately provided, thus the bathroom unit 7, a spray nozzle 12, and a rinsing nozzle 14 fitted in the bathtub 1 or a bathroom can be miniaturized to the extent possible. A detergent is sprayed and stuck into the whole bathtub 1 from the spray nozzle 12, water or hot water is sprayed into the whole bathtub 1 from the rinsing nozzle 14, and the detergent and the stains decomposed by the detergent are washed off. The water and power consumption can be saved, and the facility work is rarely required when an automatic washing device is combined with an automatic bath water boiler 17.