A flat panel speaker unit includes, within a frame (1), a transparent diaphragm (2) for outputting sound, a vibration generating part (4) for vibrating the diaphragm (2); and a display device (3) disposed inward of the diaphragm (2), for displaying information. The diaphragm (2) and the display device (3) are stacked with a gap therebetween so that an image on the display device (3) can be viewed through the diaphragm (2). The diaphragm (2) is fixed to the frame (1) by mounting a peripheral portion of the diaphragm (2) on to the frame (1).