The present invention relates to a hinge device comprising: a casing having a projection hole; a cam provided in the casing, the cam being rotatable with respect to a rotational axis, movable in the direction of the rotational axis, and undetachable from the casing, the cam having a projection projecting through the projection hole and a cam face surrounding the rotational axis; a flat spring for holding the cam face; a base movable in the direction of the rotational axis, the cam being rotatably attached to the base; and a pressing spring for urging the cam and the base toward the direction of the projection.