An ultrasonic transducer includes a housing, a driving device, and a detecting device. The housing internally includes an ultrasound transmitting/receiving unit, the housing sealing ultrasonic propagation liquid. The driving device includes a driving motor and an intermediate member. The driving device is configured to transmit a rotary driving force from the driving motor to swing the ultrasound transmitting/receiving unit. The detecting device includes a detecting member and is configured to detect an origin position serving as a reference in control of the swing of the ultrasound transmitting/receiving unit. The driving device is configured to transmit the rotary driving force to the intermediate member, extract a rotation of the intermediate member, decelerate the rotation of the intermediate member and transmit the rotation to the detecting member thereof in a route different from the driving device, and detect the rotation of the detecting member by a sensor to detect an origin position.
