PURPOSE: To provide a gate cutting device capable of automatically positioning and fixing plastic injection moldings, cutting gate portions, conveying and processing cut gate potions, and inspecting and replacing cutters.

CONSTITUTION: An articulated robot in which the end of an arm 8a can be shifted and set in any desired position through sequence control is used and a cutter 13 is freely detachably supported at the end of the arm 8a and also a gripping portion 14 for gripping cut gate portions G is provided and a molding receiving stand 7 on which moldings W are positioned and fixed, a cutter inspection device 10 for detecting the loss of each cutter due to breaking, a cutter replacement board 9 on which cutters 13 for replacement are placed, and a processing unit 11 for the gate portions G are all disposed within the movable area of the arm 8a. Even if the moldings W are fixed slightly out of position on the molding stand 7, the use of the flexible cutter 13 enables the gate portions G to be surely cut as the cutter 13 is bent.