A combustion apparatus has a fuel feed unit, a blower for supplying combustion air, a mixing unit of fuel and combustion air, a first catalyst provided downstream of the mixing unit, a first heat receiving unit adjacent to the first catalyst, a second catalyst with a large geometrical surface area than that of the first catalyst provided downstream in the flow direction of the first catalyst, an electric heater for heating the catalyst provided downstream of the second catalyst, an air permeable insulator provided downstream of the electric heater, and a second heat receiving unit provided downstream of the air permeable insulator, wherein power is supplied to the electric heater when starting combustion to heat the second catalyst over the reaction temperature of catalyst, a mixed gas of fuel and air is fed to start catalytic combustion of second catalyst, the downstream portion in flow direction of the first catalyst is heated over the reaction temperature of catalyst by the combustion heat of the second catalyst, and combustion is started by the first catalyst.