To suitably inject fuel to an injector by cooling fuel in a circulating type fuel supplying device in a small planning boat having satisfactory efficiency by a cooling device having a simple structure, and supplying fuel to the injector.

The circulating type fuel supplying device is formed in a structure having fuel in a furl tank 6 supplied to the injector 14 via a fuel-supplying pipe 17 by a fuel pressurizing pump 18, and excess fuel of the injector 14 is returned to the fuel tank 6 via a fuel-returning pipe 19. In this device, a heat exchanger 21 utilizing outside cooling water is disposed in the fuel-supplying pipe 17 between the fuel-pressurizing pump 18 and the injector 14 as a fuel cooling device. By cooling the fuel immediately prior to its entering to the injector 14, sufficiently cooled fuel can be supplied to the injector as compared with the case, where returning fuel is cooled.