PURPOSE: To prevent washing liquid in the form of mist form leaking to the outside by forming a continuously flowing curtain at a first opening through which matters to be washed are conveyed and a second opening from which the matters having been washed are discharged in such a manner that both the openings are closed by the curtain.

CONSTITUTION: In a sealed washing machine 1, a washing liquid 5a is sprayed from a spray 4 against matters to be treated 2, which are being conveyed from an opening 1a, to effect washing the matter, and thereafter the matters to be washed, after being washed, are discharged through a second opening, while continuously flowing curtains 5b, 5c are formed at the first and second openings so that both the openings are closed by the curtains. As a result, liquid in the form of mist formed in the washing machine is prevented by the curtains from leaking through the openings to the outside, with the result that contamination outside the machine is avoided and liquid in the form of mist is prevented from igniting.