Impeller-type ejectors (2) are installed on the surfaces on both sides of a cabinet (1) defining an ejection chamber in the cabinet. Shots ejected from the ejectors (2) to a workpiece and fallen are conveyed in the horizontal direction by a horizontal screw conveyor (4) positioned above the lower end of the cabinet (1) and then conveyed upward by a vertical screw conveyer (5) whose base end is above the lower end of the cabinet (1). The shots pass from the upper section of the vertical screw conveyer (5) through a chute (8) to reach an opening/closing gate (9). When the gate (9) is opened and the shots are supplied to the ejectors (2) for re-ejection, a portion of the shots is caused to overflow from the gate (9). The overflowed shots are caused to pass through a separator (11) and a sieve device (15) to remove impurities and then returned to the horizontal screw conveyor (4).