A cross-sectionally substantially-semicircular portion of an edge portion adapted to connect an outer periphery of a diaphragm to a speaker frame is configured to have an uneven-thickness structure in which the thickness of the portion gradually decreases toward a sticking portion of an outer peripheral portion of the speaker frame from a sticking portion of the outer periphery of the diaphragm. Thus, the propagation characteristic of vibrations generated on the edge portion is improved. Disturbance is prevented from occurring in an mid-range frequency characteristic due to inverse resonance caused by the edge portion.