rotating the washing spin tank 2 while supplying water in a washing process and a second process of sprinkling washing water into the washing spin tank 2 from between the outer tank 1 and the washing spin tank 2 by the rotation of the washing spin tank 2 operation of the above structure is now described referring to fig3 a c after a wash and detergent have been introduced into the washing spin tank 2 the first process of rotating the washing spin tank 2 while supplying water into the washing spin tank 2 by operating the water supply valve 10 is carried out the washing spin tank 2 is rotated at a rotational speed of r1 as shown in fig3 b until time t1 when the water level inside the washing spin tank 2 reaches a preset water level s1 shown in fig3 a when water is supplied while rotating the washing spin tank 2 in this fashion the introduced detergent starts to dissolve due to a stirring force generated by the rotation of the washing spin tank 2 and the concentration of detergent in the washing water inside the washing spin tank 2 starts to increase with the start of rotation as shown in fig3 c after passing a high concentration state in which the concentration momentarily exceeds 100 an approximately 100 concentration is finally reached this action of supplying water to a preset level while rotating the washing spin tank 2 is the first process during the period until t1 of the first process high concentration washing water gradually penetrates into the wash acting on the dirt and the washing water passes through the wash by.