an electrostatic ultrasonic transducer includes a diaphragm having a conducting layer and a pair of first and second fixed electrodes opposed to the corresponding surfaces of the diaphragm , the pair of fixed electrodes having a plurality of through holes in corresponding positions , wherein a dc bias voltage is applied to the conducting layer of the diaphragm and an alternating current signal is applied between the first and second fixed electrodes to generate an ultrasonic wave . part of the pair of fixed electrodes includes s driving fixed electrode for driving the ultrasonic transducer , and the other part includes a detecting fixed electrode for detecting the amplitude of the diaphragm . the ultrasonic transducer includes a control unit that controls the vibration of the diaphragm so that the amplitude is proportional to the input signal based on the amplitude of the diaphragm detected by the detecting fixed electrode .