A combustion apparatus 51 includes a plurality of burners 58, a plurality of fuel supply channels 89, a blower 53, an air supply passage 37, and a pressure regulator 56. The burners 58 are divided into a plurality of burner groups 71. The pressure regulator 56 is branched at a portion located immediately after a gas outlet 31 at downstream of the regulator 56 and connected to the respective fuel supply channels 89, so as to regulate gas supplied at a primary pressure to gas at a secondary pressure in response to a predetermined signal pressure sensed from one selected from a part of the air supply passage 37 and the blower 53 and to discharge the regulated gas through the pressure regulator 56. The fuel supply channels 89 each are configured to perform fuel supply to the respective burner groups 71 and are provided with a switching valve 75 for either shutting off or reducing the fuel supply to at least a part of the burner groups 71.