A spring hook structure interposed between a fixed member and a movable member rotatably supported on the fixed member, the spring hook structure comprising: a torsion coil spring comprising a coil portion, a first arm extending from one side of the coil portion, a second arm extending from the other side of the coil portion, a tip portion of the first arm bent substantially at a right angle, and a tip portion of the second arm bent substantially at a right angle; a rotation support pin by which the movable member is rotatably supported on the fixed member, the rotation support pin being inserted into the coil portion; a first hook surface on which the tip portion of the first arm is hooked, the first hook surface being formed in the fixed member; a second hook surface on which the tip portion of the second arm is hooked, the second hook surface being formed in the movable member, characterized by: a first regulation wall placed in the fixed member at a position not interfering with the tip portion of the first arm moving along the first hook surface when the coil portion is subjected to flexural deformation but interfering with the tip portion of the first arm moving along the first hook surface when the first arm is subjected to flexural deformation; and a second regulation wall placed in the movable member at a position not interfering with the tip portion of the second arm moving along the second hook surface when the coil portion is subjected to flexural deformation but interfering with the tip portion of the second arm moving along the second hook surface when the second arm is subjected to flexural deformation, wherein, when the movable member rotates about the rotation support pin, the first regulation wall prevents the tip portion of the first arm from moving along the first hook surface once the tip portion of the first arm starts moving along the first hook surface while the first arm is subjected to the flexural deformation, and the second regulation wall prevents the tip portion of the second arm from moving along the second hook surface once the tip portion of the second arm starts moving along the second hook surface while the second arm is subjected to the flexural deformation. a torsion coil spring comprising a coil portion, a first arm extending from one side of the coil portion, a second arm extending from the other side of the coil portion, a tip portion of the first arm bent substantially at a right angle, and a tip portion of the second arm bent substantially at a right angle; a rotation support pin by which the movable member is rotatably supported on the fixed member, the rotation support pin being inserted into the coil portion; a first hook surface on which the tip portion of the first arm is hooked, the first hook surface being formed in the fixed member; a second hook surface on which the tip portion of the second arm is hooked, the second hook surface being formed in the movable member, characterized by: a first regulation wall placed in the fixed member at a position not interfering with the tip portion of the first arm moving along the first hook surface when the coil portion is subjected to flexural deformation but interfering with the tip portion of the first arm moving along the first hook surface when the first arm is subjected to flexural deformation; and a second regulation wall placed in the movable member at a position not interfering with the tip portion of the second arm moving along the second hook surface when the coil portion is subjected to flexural deformation but interfering with the tip portion of the second arm moving along the second hook surface when the second arm is subjected to flexural deformation, wherein, when the movable member rotates about the rotation support pin, the first regulation wall prevents the tip portion of the first arm from moving along the first hook surface once the tip portion of the first arm starts moving along the first hook surface while the first arm is subjected to the flexural deformation, and the second regulation wall prevents the tip portion of the second arm from moving along the second hook surface once the tip portion of the second arm starts moving along the second hook surface while the second arm is subjected to the flexural deformation. a first regulation wall placed in the fixed member at a position not interfering with the tip portion of the first arm moving along the first hook surface when the coil portion is subjected to flexural deformation but interfering with the tip portion of the first arm moving along the first hook surface when the first arm is subjected to flexural deformation; and a second regulation wall placed in the movable member at a position not interfering with the tip portion of the second arm moving along the second hook surface when the coil portion is subjected to flexural deformation but interfering with the tip portion of the second arm moving along the second hook surface when the second arm is subjected to flexural deformation, wherein, when the movable member rotates about the rotation support pin, the first regulation wall prevents the tip portion of the first arm from moving along the first hook surface once the tip portion of the first arm starts moving along the first hook surface while the first arm is subjected to the flexural deformation, and the second regulation wall prevents the tip portion of the second arm from moving along the second hook surface once the tip portion of the second arm starts moving along the second hook surface while the second arm is subjected to the flexural deformation.