A speaker device includes a vibration system, having a voice coil bobbin, a diaphragm, a supporting cap and a cap, and a magnetic circuit system. The inner peripheral edge portion of the diaphragm is mounted on an area in the vicinity of the upper end portion of the outer peripheral wall of the voice coil bobbin. The projecting portion of the cap is inserted into the opening of the supporting cap, and the supporting cap is placed under the cap. Each of the projecting portions of the cap is fixed to each of the correspondent recessed portions of the diaphragm, and the claw portion of the cap is fixed to the projecting portion of the diaphragm and the third flat portion.