A hinge device increases an open angle of a second member relative to a first member without enlarging the hinge device. A first pulley is fixed to a first mounting member mounted on the first member. A second pulley is fixed to a second mounting member mounted on the second member. A timing belt runs between the first and second pulleys. One end of a connecting member that connects the first mounting member to the second connecting member connects rotatably to an axis part of the first mounting member, with the opposite end connected rotatably to an axis part of the second mounting member. Pins to that abut to the outside of the timing belt are provided such that the width between one side and the opposite side of the timing belt becomes smaller than the diameter of at least one of the first pulley and the second pulley.