A first hinge 11 comprises: a first turning shaft portion 111 which extends vertically; a first supporting portion 112 which is extended longitudinally and laterally, and supports the bottom of the first turning shaft portion 111; and a first mounting portion 113 which extends downwardly from the rear end of the first supporting portion 112. A second hinge 12 comprises: a second turning shaft portion 121 which extends vertically; a second supporting portion 122 which is extended longitudinally and laterally, and supports the top of the second turning shaft portion 121; and a second mounting portion 123 which extends upwardly from the rear end of the second supporting portion 122. The first supporting portion 112 is disposed above the second supporting portion 122. The first mounting portion 113 is disposed below the second supporting portion 122. The second mounting portion 123 is disposed above the first supporting portion 112.