A movable member (not shown) non-turnably connected to a second hinge member is arranged on the turning axial line of first and second hinge members such that the movable member is turnable and movable in the direction of the turning axial line. The movable member is biased toward the first hinge member by a coiled spring (not shown). A confronting surface of the first hinge member with respect to the movable member is provided with a pair of raised wall surfaces 11d, 11d extending in the direction of the turning axial line and end face cams 41 arranged between the pair of raised wall parts 11d, 11d, respectively. A confronting surface of the movable member with respect to the first hinge member is provided with a pair of abutment arm parts 42a for converting the biasing force of the coiled spring to a turn biasing force for turning the movable member by being press-contacted with the end face cam 41. A recess 11e is formed in a lower part of the raised wall surface 11d. A side surface of a lower side of this recess 11e is provided as a part of the end face cam 41.