The present invention provides a hinge for opening/closing a door, comprising: left and right plates respectively coupled to the door and a door frame; a main housing formed in the center of any one of the left and right plates; upper and lower auxiliary housings respectively formed at the top and the bottom of the other of the left and right plates; a support member coupled to and linked with the main housing by penetrating into any one of the upper and lower auxiliary housings; a guide member coupled to and linked with the other of the upper and lower auxiliary housings, formed by inserting a portion thereof into the main housing, and having a screw hole for adjustment; an adjustment member having a screw bar for adjustment and a screw bar for fixing, which are formed to have different screwing directions as a right-handed screw and a left-handed screw, and having an adjustment space for interference prevention between the screw bar for adjustment and the screw bar for fixing; a fixing member for fixing the adjustment member by closely attaching, to the guide member through the adjustment space, the screw bar for fixing the adjustment member; and a twist spring connectedly provided between the support member and the adjustment member so as to change the strength of elasticity by the rotation of the adjustment member.