A second hinge plate supported pivotally on a first hinge plate using a shaft member so as to open and close. In the second hinge plate, a bracket is molded integrally at the upper edge of the end opposite the shaft member. A vertical shaft of a hold-stay rod is loosely fitted into a shaft hole of the bracket so as to move rotationally and slide in a vertical direction. A horizontal shaft of the hold-stay rod is inserted into a guide hole of a guide plate welded to the first hinge plate and slidable, and a stopper is folded and formed at the leading end of the hold-stay rod. The stopper is inserted into an engaging hole by movement from a guide to a receiving plate due to the opening movement of the second hinge plate and can be taken out from the engaging hole by a pushing-up operation.