PURPOSE: To enable washing of waste sand and screenings to be performed rapidly and effectively by providing an agitating impeller and a high-pressure washing nozzle to a washing vessel and providing predetermined baffle plates.

CONSTITUTION: Waste sand or screenings are supplied to a washing vessel 1 by a carrying-in machine 7 and washing water W is supplied thereto; at the same time, they are agitated by the agitating impeller 2 provided on the surface on both insides of the washing vessel 1, washing nozzle 3, for washing. In addition, a baffle plate 4 is provided in the transfer direction from the position of the agitating impeller adjustably of its mounting angles to control the water flow of the washing vessel, and to prevent the washing water, waste sand and screenings agitated and washed by the agitating impeller 2, from short-passing to the next separating zone, and to cause them stagnate for a predetermined washing time. Thence, the washed waste sand and screenings are separated to organic material and inorganic surface which are then discharged respectively to outside of the vessel by a dust remover 5 and a carry-out machine 6 for purified sand.