A movable member 6 is connected to a first hinge member 2 such that the movable member 6 is unable to turn but able to move in the axial direction. A hammer member 7 is non-turnably connected to a second hinge member 3. The movable member 6 is caused to abutted against the hammer member 7 by a coiled spring (not shown). A force conversion mechanism (not shown) is disposed between contact surfaces of the movable member 6 and hammer member 7 and adapted to convert a biasing force of the coiled spring to a force for turning the hammer member 7. An abutment projection 32 is formed on an outer periphery of the second hinge member 3. An abutment recess 71 into which the abutment projection 32 is fitted is formed in an outer periphery of the hammer member 71. A width 2 of the abutment recess 71 is set slightly larger than a width W1 of the abutment projection 32 so that the hammer member 7 can be turned relative to the second hinge member 3 to that extent.