Disclosed herein is a hair iron having upper and lower casings, a heat generating unit and a hinge connection unit. The hinge connection unit includes a hinge box secured to either of the upper and lower casings. First and second movable members each having a hinge shaft are provided in the hinge box, and move between a hinge coupling position and a hinge releasing position. An elastic member is elastically provided between the first and second movable members, and exerts an elastic force so that the hinge shaft moves to the hinge releasing position. A hinge-coupling retaining means is manipulated on an outside of the hinge box to move the hinge shaft to the hinge coupling position and simultaneously retain the hinge shaft in the hinge coupling position. A hinge-shaft connection lug is provided on a remaining one of the upper and lower casings, and has a hinge hole.