An engine (100) can handle a premixed combustion method and a diffusion combustion method. This engine (100) comprises main fuel injection valves (79), pilot fuel injection valves (82), a liquid fueltank (33), a main fuel supply path (121), a pilot fuel supply path (122), a pilot fuel filter (141), a pilot fuel high-pressure pump (56), a pilot fuel tank (171), and a pilot fuel supply pump (173).Pilot fuel that was sent from the pilot fuel high-pressure pump (56) and was not injected by the pilot fuel injection valves (82) is collected in the pilot fuel tank (171). This pilot fuel is sent toward an automatic backwashing type filter (174) and the pilot fuel filter (141), without passing through the liquid fuel tank (33).