An ultrasonic transducer including: a fixed electrode; a vibrating film placed opposite to a surface of the fixed electrode and having a conducting layer; a member that holds the fixed electrode and vibrating film; the fixed electrode including a driving-use fixed electrode formed to drive the ultrasonic transducer, and a detecting-use fixed electrode formed to detect an amplitude of the vibrating film; and a unit that controls a signal to be applied to the driving-use fixed electrode based on a magnitude of the amplitude of the vibrating film detected by the detecting-use fixed electrode so that the magnitude of the vibration of the vibrating film becomes in proportion to an input signal, wherein when an alternating current signal is applied between the fixed electrode and the conducting layer of the vibrating film, the ultrasonic transducer generates an ultrasonic wave.