PURPOSE: To carry out a plurality of moldings by combining molding sections of both of a fixed mold and a movable mold in which a plurality of molding sections are formed in various kinds by means of rotation of the movable mold.

CONSTITUTION: A steel ball 2 is disposed on a central recessed section 34a of a primary cavity 34 of a fixed mold 30, and a primary cavity 48 of a movable mold 31 is mold clamped facing the cavity 34. Molten resin is filled from a primary injection device into the cavities 34 and 48. Then, mold opening is carried out, and a primary molded product 13 is released out of the fixed mold 30 by a pin 12 while being installed on the movable mold 31. The movable mold 31 is rotated by 90°, and a secondary molding section 33 of the fixed mold 30 and a primary molding section 48 of the movable mold 31 are faced each other and mold clamping. The movable mold 31 is rotated by 90° after mold clamping again, and said secondary molding section 33 and a secondary molding section 49 of the movable mold 31 are faced each other, and molten resin is filled from a secondary injection device into secondary forming sections 33 and 49 after mold clamping. Thus a material ball composed of a steel ball 2 with a first resin layer 3 and a second resin layer 5 wrapping the periphery of said first layer is manufactured.