A rear portion of a chain transmission member (21) is connected to a push/pull drive device (19) disposed in the rear portion of the metal mould replacing stand (3) while a front portion of the transmission member (21) is connected to the advancing/retreating member (22). A guide rail (23) for accommodating the transmission member (21) and the advancing/retreating member (22) is placed in the upper portion of the replacing stand (3) so as to extend in the fore and rear direction. A front portion of a hook (28) is supported vertically swingably by a front portion of the advancing/retreating member (22) through a pin (29) and a concave engaging portion (30) is formed in the rear swingable portion of the hook (28) so as to face upward. An engaged portion (34) is formed in the rear portion of the metal mould (7) so as to project downward and the engaging portion (30) is adapted to be engaged with the engaged portion (34) by means of a spring (36) from below.