WASHING MACHINE

The present invention provides a washing machine configured such that a gas having a cleaning function is prevented from leaking to the outside. The washing machine performs an ozone cleaning step for cleaning dry laundry by supplying ozone to the laundry prior to a washing step. Before the start of the ozone cleaning step, a dehumidification water valve (14) is opened to once retain dehumidification water in a bottom of an outer tub (7). Then, water is retained in an overflow trap (45) by utilizing the dehumidification water, whereby a flow passage extending from the outer tub (7) to the outside is sealed with the water. Further, a detergent valve (55) or a finishing agent valve (56) is opened to retain water in a water supply trap (24), whereby a flow passage extending from the outer tub (7) to the outside is sealed with the water.