To reduced the production cost of a mold by a method wherein a vent member equipped with fine holes is fitted to the inlet of each suction hole and the fine holes of the vent member are formed by a plurality of grooves formed on the outer peripheral part of a bar-like part.

A vacuum suction part 10 consists of a sucking hole 11 formed in a movable mold 3, bottoms 12 and holes 13 formed at the inlets of the sucking hole 11 and vent members 20 fitted to the holes 13. The vent member 20 is formed by providing a plurality of grooves 23 on the outer peripheral part 22 of a vent main body 21, which is a bar-like part, one edge face 24 of which contacts with the bottom 12 and on the other edge face 25 side of which a mold surface 26 is formed. The groove 23 and the inner surface wall of the hole 13 forms a fine hole 27, the diameter of which is enough smaller than the diameter d of the sucking hole 11. Since the fine holes can be obtained by a simple structure, in which the hole 13 is plugged by fitting a bar-like part into the hole 13, the number of parts comprising a mold becomes fewer, resulting in allowing to reduce the production cost of the mold.