It becomes possible to obtain high sound pressure in a high frequency domain by a capacitive ultrasonic transducer which comprises a membrane 9 on which one electrode 7 is formed, a cavity 13 constructed in its backface, and a substrate 2 on which these are mounted and supported and on whose surface an electrode 12 is provided, on a surface in an ultrasonic transmission and reception side, characterized in that the membrane 9 comprises two or more layers, and at least one layer of them comprises a high dielectric constant film 8.
