A display device (3) is used for a number-of-fish counting system for counting the number of fish. The display device (3) is provided with a display unit (31) that displays a plurality of selectable instruction items on a main screen MS. The plurality of instruction items include a recording instruction item (D1) that instructs a processing device of the number-of-fish counting system to execute or stop recording of video of fish, and an analysis instruction item (D2) that instructs the processing device to count the number of the fish by analyzing the fish on the basis of the recorded video.