To provide a spacer capable of facilitating installing works and surely installing.

An installing spacer 10 inserted in a dash silencer is provided with a hollow cylinder-shaped trunk portion 12, a first flange 13 extending from an one end portion to an outside of the trunk portion in a radial direction, a second 14 (Contact face flange) extending from an other end portion to an outside of the trunk portion in a radial direction, and a plurality of fixing claws extending toward a direction from the outside of the other end portion of the trunk portion to the first flange. The fixing claw is comprised of an elastic fixing claw 17 and a rigid fixing claw 18. The contact face flange is easily pushed into so that an outer diameter of the contact face flange is relatively smaller. Further, the fixing claws 17 and 18 are pushed in a state that the center of the spacer is located at the center of an installing hole so that the fixing claws are extended to the upper and the outside. After installing the fixing claws, the elastic fixing claw 18 fixes the spacer by keeping in contact with a lower surface of a rubber sheet 8 of the dash silencer 7.