This invention relates to a liquid fuel combustion apparatus such as oil space heater in which liquid fuel is vaporized by a vaporizer and the vaporized liquid fuel is injected through a first nozzle to a burner. The vaporizer is heated by combustion of fuel gas which is injected through a second nozzle to the burner before the vaporizer has been heated up to a temperature at which the liquid fuel passing the vaporizer is evaporated. The injection of the fuel gas from the second nozzle to the burner is changed to the injection of the vaporized liquid fuel from the first nozzle when the vaporizer has been heated up to a desired temperature. The supply of the liquid fuel to the vaporizer is carried out by a fuel pump which is driven by electric power generated by a thermopile.