a clamp includes a fitting portion to be fixed to an object to be attached ; a clamp portion having a substantially u - character shape connected to the fitting portion ; a first receiving portion for receiving a rod - shaped member through an insertion port ; and a second receiving portion for receiving a rod - shaped member through an insertion port of the clamp portion and passing through the first receiving portion . an elastic piece extends from an inner wall of the clamp portion to hold the first rod - shaped member together with the first receiving portion . a stopper extends from the inner wall of the clamp portion to hold the second rod - shaped member together with the second receiving portion and to prevent the first rod - shaped member from entering the second receiving portion .