PURPOSE: To avoid inconvenience of an occurrence of defective water supply or overflow of pooled washing water by providing a filter and a water pool section with the first and the second water level detective means and causing the water supply stop signal to be outputted when either the first or second water level detective means outputs the specified signal corresponding to a specified water level.

CONSTITUTION: When the H signal from the flip-flop circuit 97 is inputted to the AND circuit 96 by operation of the start-up switch, the transistor 98 is turned on by the H signal from the AND circuit 96. And, the relay 99 inserted in the collector circuit of the transistor 98 is energized, leading the switching valve 22 to open. When the water level in the water pool section 23 reaches a specified level and the H signal is inputted from the pressure sensor 91 in the filter or the water level sensor 92 in the water pool section 23 to the NOR circuit 95, the L signal is inputted from the NOR circuit 95 to the AND circuit 96, thereupon, the transistor 98 is switched off, the switching valve 22 is shut and the flip-flop circuit 97 is reset. Even when either the pressure sensor 91 or the water level sensor 92 becomes out of order, the water level-detective capacity can be maintained with the output from the NOR circuit 96.