To make it possible to easily grasp a race course even in environment wherein sufficient lightness can not be obtained, e.g. in nighttime or indoors by providing linear display units underwater at predetermined positions in the race course and making them illuminate.

The linear display units 3A and 3B are arranged underwater at the specific positions in the race course and illuminate in specific colors such as red, yellow, and blue to make a guide display of the race course. The display unit 3A is arranged at the outer peripheral parts of turn marks 1A and 1B where lighting is apt to be deficient at the race course peripheral part (bank side). The display unit 3B is arranged at the outer peripheral part (bank side) of the home stretch and back stretch where lighting is apt to be deficient at the race course peripheral part. Consequently, the position of the peripheral part of the race course can distinctively be displayed to racers even in environment wherein sufficient lightness can not be obtained, e.g. in nighttime or indoors. Further, the display units 3A and 3B are made to illuminate in red, yellow, etc., to make a warning display indicating that the outside of the display units 3A and 3B is a dangerous zone.