PURPOSE: To simply replace a receiving mouth processing mold within a short time by providing lateral guides guiding the mold attaching plates of a plurality of receiving mouth processing mold assemblies to the freely up-and-down movable lift base provided to the mold replacing device of a processing machine and fixing the slid receiving mouth processing mold assembly by a fixing means.

CONSTITUTION: A lift base 14 is mounted on a mold replacing device 7 provided by a processing machine 5 in a freely up-and-down movable manner and four receiving mouth processing mold assemblies A, B, C, D are mounted on the lift base 14. Different receiving mouth processing molds 52-55 are provided to the mold attaching plates 51 of the mold assemblies and the mold attaching plates 51 are provided to the lateral guides 21 arranged on the lift base 14 in a freely slidable manner. When the mold is replaced, the receiving mouth processing mold assembly C is slid to the left by a lateral slide cylinder 25 to be transferred to the lateral guide 21 on the side of the mold replacing device 7 and fixed by a hydraulic clamp 76. Next, the receiving mouth processing mold assemblies A, B, D are selected by the lift base 14.