To reduce an amount of used water and solve a problem of drainage in a blast washing device which washes plastic or light metal dishes by using sodium bicarbonate as washing agent.

A dish 1 is put in from a transferring port 12a onto an endlessly running net conveyor 32. The dish 1 is fed in a treatment chamber 10 first by the net conveyor 32. Washing water is showered to the upper and lower surfaces of the dish 1 from a washing water nozzle 24a in a pre-washing chamber 14, for washing out adhesion of remaining food, for instance. Sodium bicarbonate is injected from a sodium bicarbonate nozzle 26a onto the upper and lower surfaces of the dish 1 in a main washing chamber 16, for removing further remaining food or oil adhered to the dish 1. After injecting, the sodium bicarbonate is dropped on a bottom plate 13 together with the removed matter. The sodium bicarbonate is recovered into a lower side washing wather tank together with the water discharged from the pre-washing chamber 14 and a final washing chamber 18. The washing water overflowing the washing water tank, is fed to a nozzle header of the pre-washing chamber 14, and reused for pre-washing.