To reduce the embedded number of chill plates to half and the total height and width of a mold by making a constitution having substantially the same height as the mold height and half slitting type cavity of each member to be chill-treated in the upper surface side and the lower surface side.

The plural cavities 11, 12 corresponding to a shaft part 17 of cam shaft are arranged sideward so as to parallel to the longitudinal direction, and the half shape of the shaft part 17 is formed with molding sand 16 in the mold 15 so as to position to the upper and the lower surfaces. The chill plate 10 is arranged to a prescribed position so as to cross at the right angle to the shaft part 17. The upper and the lower ridges 13, 14 of the chill plate 10 correspond to the parting surfaces of the mold 15, and the cavities 11, 12 are opened to the upper and the lower part. The chill plates 10 arranged to the adjacent shaft parts 17 are made to the mutually shifting relation so as to form as zigzag state. By this method, since the mutually adjacent shaft parts 17, 17 are made to approach, the mold 15 can be compacted in comparison with the number of the cast cam shafts.