PURPOSE: To thin an electric and acoustic converter by making the bottom area of the air chamber of a diaphragm larger than the area of the front surface of the diaphragm, and lowering the height of the air chamber by the size that the bottom area of the air chamber is made larger.

CONSTITUTION: A diaphragm 2A is disc-shaped, and a disc-shaped piezoelectric plate 2B is adhered to the central part of the face of the diaphragm 2A. A case 3 is constituted by overlapping a lower side case body 4 on an upper side case body 5, and a short dimension cylindrical shape having an inner peripheral diameter d2 longer than the diameter d1 of the diaphragm 2A. The lower side case 4 is constituted of a lower side case body 4a whose upper edge is closed and a cover 4b covering the lower edge. And also, a front air chamber S1 and a back air chamber S2 covered with case bodies 4 and 5 are formed at both the upper and lower parts of the diaphragm 2A. Thus, the bottom area of the air chamber is made larger than the surface area of the diaphragm, so that the height of the air chamber can be reduced according as the bottom area of the air chamber is made larger, and an electric and acoustic converter can be thinned by the size that the height of the air chamber is reduced.