An electroacoustic transducer has an cup chamber and a diaphragm made of deformable electrostrictive polymer, which is attached to an opening of the chamber. The electroacoustic transducer also has first and second adaptive electrode layers formed on a front surface and a rear surface of the diaphragm, across which audio signal voltage biased by a direct-current biased voltage is applied. The first and second adaptive electrode layers have shapes that are adjustable according to a change in a shape of the diaphragm. The diaphragm is formed to make maximum a difference in air pressure of the front surface and the rear surface of the diaphragm, thereby forming any one of concave and convex shapes thereof.