PURPOSE: To reduce the number of part items of an opening/closing device by making a damper stay for operating force reduction usable as a stopper stay for hood release holding.

CONSTITUTION: One end of a damper stay 4 is rotatably mounted on an engine hood 1 by a support pin 6, and the other end is mounted on the elliptic hole 11 of a stay bracket 10 fixed to a rear pillar 2 through a pin 9 in such a manner as to be capable of sliding. The elliptic hole 11 is set to the form such that the pin 9 can be circularly slid around the mounting part of the damper stay 4 with hood side in the opened state of the engine hood 1 where the damper stay 4 is extended to the maximum, and a locking groove for fitting the slid pin 9 is set on the end part. Thus, the pin 9 which is the rotating supporting point of the damper stay 4 is slid along the elliptic hole 11 in the opened state of the engine hood 1, and separated from the hinge 3 center of the engine hood 1, whereby the moment for food holding is increased.