A vehicle-mounted acoustic apparatus includes a frame including an annular portion and a supporting portion and attachable to an opening of a partition plate between an in-cabin space and an outside-cabin space, a diaphragm vibratorily supported by the annular portion, a magnetic circuit supported by the supporting portion and having a magnetic gap, a cylindrical bobbin provided on the diaphragm with one end thereof projecting from one side of the diaphragm, a voice coil wound around the bobbin and positioned in the magnetic gap, and a rear cover member defining an air chamber provided between the rear cover member and the diaphragm. The rear cover member is vibratorily supported and allows back pressure to be conducted to the outside-cabin space. An air path between the air chamber and the in-cabin space follows a route passing through a space on an inner side of the bobbin.