To eliminate the need for the manpower of washing work and to improve the washing capacity and productivity by successively executing a shower washing to spray a washing liquid and an ultrasonic washing with a surfactant and in pure water, then executing dehydration and drying.

This method consists of respective stages for the shower washing to spray the washing liquid from a nozzle, the ultrasonic washing using the surfactant aqueous solution as the washing liquid, the shower washing to spray the pure water from the nozzle, the ultrasonic washing to use the pure water as the washing liquid, dehydrating and drying. The high washing capability may be obtained by executing the ultrasonic washing by taking the arrangement of the wash in shower washing and washing tanks and the flow of the washing liquid into consideration. The washing device is successively arrayed with the shower washing device 121, the ultrasonic washing device 122 using the aqueous surfactant solution, the shower washing device 123 using the pure water, ultrasonic washing device 124 using the pure water, the shower washing device 123 using the pure water, the dehydrating device 125 and the drying device 126 on a washing device stand 120.