To provide an excellent sounder which is used for various moving body communication terminals, etc., and generates calling sounds of a high sound pressure.

This sounder is provided with notched parts 13c and 13d in the lower parts on the opposite side of the wall parts of a resonance cover 13 and is made larger in the diameter of a diaphragm 12 up to these notched parts 13c and 13d. The diameter of the diaphragm 12 is made larger up to the notched parts 13c and 13d, by which the volume of an air chamber 13f is increased and the sound production output is improved by these notch parts 13c and 13d.