To store a speaker unit and spare tire in a tire storage unit without causing troubles in handling the spare tire and sound output.

This speaker unit comprises: a frame with openings; a sound output unit installed inside the frame; and an elastically deformable annular gasket that is attached to the frame and projects outward from the frame. The speaker unit is housed inside a tire storage unit, which has a recessed storage part that opens up upward so as to allow a spare tire to be stored therein, in such a manner that the gasket is pushed against the rim part of the wheel of the spare tire at a position below the disc part of the wheel. Consequently, two spaces surrounded by the gasket, the respective parts of the wheel, and the tire storage unit are formed. Thus, high-quality sound can be output from the speaker unit, and there is no need to remove the speaker unit from the tire storage unit when storing or removing the spare tire into/from the tire storage unit.