To prevent the breakage of molding in a sand mold with slow shifting speed of carriers for molding board in the same cycle time by arranging opening/closing roller mechanisms at the position of the both end outsides of the upper roll in the upper and the lower rolls in two steps and engaging with the lower surfaces of the carriers for molding board.

The carrier 8 for molding board loading the sand molds 9 on the rollers in the opening/closing roller machine 10 at the left side is carried in under condition of engaging and supporting with the lower surface of the carrier. The empty carrier 8 for molding board is carried in on a lifter table 5 with rails at the right side. The upper part of the lifter table 5A with rails at the left side empties. The roller is opened together with a turning arm 17 by working a horizontal cylinder 16 of the opening/closing machine 10 at the right side and the rails on the lifter tables 5, 5A are risen to the levels of the upper rails 1 and the lower rails 2 by working cylinders 3, 3A. The carrier 8 for molding board on the lifter table 5 is received by closing the opening/closing machine 10 at the right side and the carrier 8 for molding board loading the sand mold 9 is delivered to the lifter table 5A by opening the opening/closing roller machine 10 at the left side.