Abstract: A waste oil combustion apparatus can use various kinds of waste oils and burn the same efficiently, and permits effective utilization of the thermal energy resulting from the combustion thereof. The apparatus includes a bottomed cylindrical combustion furnace, a waste oil supply unit for supplying waste oil into the furnace, an auxiliary-fuel supply unit for supplying auxiliary fuel for burning the waste oil in the furnace, an ignition burner for heating the furnace inside and the waste oil and auxiliary fuel to ignite the fuels, an air supply unit for supplying air to the furnace, and a controller for controlling each of the igniting burner, waste oil supply unit, auxiliary-fuel supply unit and air supply unit to act at a predetermined time and operate for a predetermined time. The waste oil is spirally swirled inside the furnace under the action of air from the air supply unit.