To reduce washing nonuniformity and to sharply improve washing efficiency by subjecting a washing basket to turning oscillation within a prescribed angle in the horizontal direction in a washing liquid in a washing vessel while vertically moving the washing basket.

When a washing basket 3 is at the lowest position in its vertical movement range, levers 27, 28 each fall right beneath. By the drive of a motor, the first and second levers 27, 28 are rotated at uniform velocity in the direction of the arrow A and in the reverse direction of the arrow A' respectively, thus raising both ends of the washing basket 3 at uniform velocity by uniform distance. Until this state is reached, while the washing basket 3 is raised with its horizontal state being maintained, it is rotated around an imaginary axis S to a prescribed angle θ in the direction of the arrow R. Since the washing basket 3 is thus subjected to turning oscillation within a prescribed angle range every rising and lowering, the flow of washing liquid in contact with the surface of a material to be washed is made in multi-directional.