To prevent a metal plate from being deformed and to facilitate removal of it by providing a projected line on either a mold main body or the back face of the metal plate and a recessed line on another one and performing hooking and release of hooking of the metal plate by sliding the metal plate along the mold main body.

A fixed mold 2 and a movable mold 3 being a mold main body are provided and a cavity 4 is provided along the both faces. A recessed part 5 is provided on the face facing to the cavity 4 on the fixed mold 2 and a metal plate 6 is mounted therein. A dovetail recessed line 8 is provided on the back face of the metal plate 6. In addition, the metal plate 6 is slid along the bottom face of the recessed part 5 and the dovetail projected line 7 and the dovetail recessed line 8 are joined together to mount the metal plate 6 on the fixed mold 2. When the metal plate 6 is exchanged, after the movable mold 3 is separated from the fixed mold 2, the metal plate 6 is slid along the extending direction of the dovetail projected line 7.