A device is mounted on a vehicle body and housed in a space between a pillar inner and a pillar trim. A speaker is inserted into an opening portion opened in the pillar trim from an inside of a vehicle compartment and retained therein. A harness is connected to the speaker and disposed in the space. In a part of the speaker to be inserted into an inner side of the pillar trim, a protrusion portion is provided that protrudes radially outward. An insertion acceptance portion that is a gap for accepting insertion of the protrusion portion is provided in an opening edge portion facing the opening portion on an inner surface side of the pillar trim. The insertion acceptance portion has a width larger than a width of the protrusion portion.