A capacitive electromechanical transducer includes a substrate, a cavity formed by a vibrating membrane held above the substrate with a certain distance between the vibrating membrane and the substrate by supporting portions arranged on the substrate, a first electrode whose surface is exposed to the cavity, and a second electrode whose surface facing the cavity is covered with an insulating film, wherein the first electrode is provided on a surface of the substrate or a lower surface of the vibrating membrane and the second electrode is provided on a surface of the vibrating membrane or a surface of the substrate so as to face the first electrode. In this transducer, fine particles composed of an oxide film of a substance constituting the first electrode are arranged on the surface of the first electrode, and the diameter of the fine particles is 2 to 200 nm.