To provide an ultrasonic fish finder having interference suppressing function, capable of completely separating the reflected wave of ultrasonic waves of own finder from the reflected waves of the ultrasonic waves of the other finder and suppressing interferences.

An infrared irradiating section 2, an infrared sensor 3 and an ultrasonic oscillator 4 are fixed to a transmitting and receiving sensor 1, the present ultrasonic oscillator 4 is connected to a transceiver 5, and the infrared irradiating section 2 is connected to a signal-transmitting function 6a of a controller 6 consisting of a CPU. In addition, an infrared sensor 3 is connected to an infrared detecting function 6b of the controller 6, the transceiver 5 is connected to a signal-processing function 6c of the controller 6, and the signal-processing function 6c is connected to a display device 7.