To expand a space of a back chamber, to improve the response characteristic of sensitivity and a frequency, and to simplify processes to reduce process cost by integrating a first base for performing an insulating function by a conventional electret capacitor microphone with a second base for performing a conductive function.

This microphone is constituted in such a way that a metallic plate layer is formed on both surfaces of a cylindrical body having the inside consisting of a hollow circumferential insulator so that the body has an outer diameter smaller than the outer diameter of a circumference, and that the metallic plate layer may be conducted by a conductive patterns 278 formed by plating the inside surface of the circumference, a through hole 276 or a via hole. The first base having the insulating function and the second base having the conductive function in the conventional microphone are integrated into a single base 270.