A method and device for displaying an underwater detection image is provided, in which an ultrasonic signal having a predetermined beam width is periodically transmitted underwater, receives a signal reflected on a detection target object which moves underwater, generates information on the detection target object based on the received signal, and displays the information on a display module. The method includes periodically detecting the detection target object and a position thereof based on the received signal, coupling the same detection target objects by associating the same based on the detection target object and the position periodically detected, and associating a displacement symbol corresponding to a change in a position of the detection target object with the coupled detection target object, and displaying the displacement symbol at the detected position of the detection target object at least on a two-dimensional position coordinates displayed in the display module.