A silencer includes a smaller cylindrical member having a planar portion and a larger cylindrical member arranged to closely contact at least a portion of the outer circumferential surface of the smaller cylindrical member. The larger cylindrical member as seen in a direction orthogonal to its axis provides an oblate cross section having a major axis X and a minor axis Y and the smaller cylindrical member is arranged to have the planar portion traversing the major axis X of the larger cylindrical member.