PURPOSE: To unnecessitate the removing work of remained sand and to improve the working ratio by arranging a discharging hole having an opening/closing discharging gate in a sand bin connected to the discharging side of the kneading chamber.

CONSTITUTION: An additive is added into the sand supplied from a raw material sand tank 1 from a nozzle 6 in a supplying hole 4. This sand is continuously kneaded in the kneading chamber 3 and discharged. Then the sand bin 11 is provided by connecting it to the discharging side of the kneading chamber 3. The discharging hole 5 having the opening/closing gate 9 is provided in the sand bin 11. The opening/closing gate 9 is operated by a cylinder 10 to control the discharging amount of the sand. By this method, the start and the stop of a driving motor can optionally be executed.