To facilitate the installation work of a muffler at the narrow place of an installation space.

Two body supports 12 are projected from a side member 10 toward the right/left directions of a vehicle. Support rods 23, 25 are projected from the front/rear end surfaces of a muffler 20 along the axis line direction of a main body 21. A first installation hole 31 penetrated in a lateral direction and a second installation hole 32 penetrated in a vertical direction are provided in a support rubber 30 while shifting vertically each other. By inserting the body support 12 of the side member 10 to the first installation hole 31 of the support rubber 30 and also inserting the support rods 23, 25 of the muffler 20 to the second installation hole 32, the muffler 20 is installed on the side member 10.