PURPOSE: To collapse a casting mold easily by passing wet air through the casting mold in which molten metal is charged to wet the sand then shaking out the molding sand.

CONSTITUTION: Many molding flasks 2, 2 contg. casting molds M1 in which molten metal is charged are moved horizontally and one piece among the molds is stopped temporarily between an air feed box 1 and an air suction box 6. The box 1 is moved downward and the box 6 is moved upward by extending cylinders 3, 7, so that the bottom surface of the box 1 is brought into tight contact with the top surface of the flask 2 and the top surface of the box 6 with the bottom surface of the flask 2, respectively. In succession, a stop valve 5 is opened to induce humidified air into the box 1 and a stop valve is opened to suck and evacuate the air in the recess of the box 6. The humidified air passes through the inside of the mold M1 and the mold M1 is wetted. The valve 5 is closed after the wetting operation for a prescribed time and the cylinders 3, 7 are retracted to move the box 1 upward and the box 6 downward. The wetted mold M1 is thoroughly collapsed simply by shaking out of molding flask.