A piezoelectric electro-acoustic transducer has a substantially decreased resonant frequency without having to modify the size of a piezoelectric diaphragm or the shape of casing members used therein. The piezoelectric electro-acoustic transducer has a piezoelectric diaphragm including a metal plate and a piezoelectric ceramic disc disposed on one surface of the metal plate, wherein the piezoelectric diaphragm is to be supported at its periphery. A plurality of projections are specifically provided for stress transmission suppression at the periphery of the piezoelectric diaphragm in order to suppress or eliminate occurrence of circumferential transmission of a stress at the periphery during activation of the transducer.