A flasher type fish sonar includes a front case in which a display window is formed in front, a rotary disc opposite to the display window rotated by a motor, an ultrasonic transducer for transmitting ultrasonic waves in the water by a control portion and for receiving reflected signals in the water, a display signal transmitting portion for transmitting reflected signals received by the ultrasonic transducer and display data forming formed by the control portion and for transmitting the same to the rotary disc, a display control portion attached to the rotary disc, a fish sonar display portion displayed by light emitting diodes attached near an edge of the rotary disc, and a letter illustration numeral display portion displayed by light emitting diodes inside of center portion of the rotary disc.