A tension member for use in an anchor method, in which both ends of the tension member are held by anchors, is released by cutting all or some of the wires in the tension member and then hitting at least one of the cut wires to release the tension member. The anchor includes an anchor head having a wedge-receiving space, a wedge unit seated in the wedge-receiving space, and three wedges assembled together to form a hole at the center of the wedge unit, through which the tension member is inserted. A support plate is inserted into a groove formed at an upper portion of the first hole and an O-shaped ring is provided around the wedges so that the wedges are expanded around the support plate. A spring is positioned on the wedge unit for constantly biasing the wedge unit against the wedge-receiving space.