An ultrasonic transducer includes: a fixed electrode having corrugations on the surface; a vibrating film having an electrode layer and disposed on the surface of the fixed electrode; and a holding member which holds the fixed electrode and the vibrating film. The ultrasonic transducer is driven by applying an AC signal between the electrode layer of the vibrating film and the fixed electrode, and generates a sound pressure of at least 120 dB within a frequency range from 20 kHz to 120 kHz.