Abstract: This invention provide a fuel heating apparatus for engines using a heavy oil as a fuel, wherein the heavy oil is heated by utilizing the exhaust gas energy so as to promote an increase in the fluidity thereof. This fuel heating apparatus can be applied to a diesel engine in which a heavy oil is injected from fuel injection nozzles into combustion chambers by an operation of a fuel injection pump to which the heavy oil is supplied from a fuel tank through a fuel passage. An exhaust gas passage to which the exhaust gas from the combustion chambers is discharged is connected to a heat exchanger provided in the fuel tank and a heat exchanger provided around the fuel passage, and the heavy oil in an outlet region of the fuel tank and that flowing in the fuel passage are heated with the energy of the exhaust gas. Thus, the heavy oil is fluidized, and the injection of the heavy oil from the injection nozzle into the combustion chamber is done smoothly.