A combustion apparatus has a burner including a burner body and a combustion plate, as well as a combustion box. A combustion plate flange part projects outward beyond an inner rim of a body flange part and beyond an inner rim of a combustion box flange part. A packing has a portion interposed between the combustion plate flange part and the body flange part, and a portion interposed between the combustion box flange part and the body flange part outside an outer rim of the combustion plate flange part. A distribution plate having formed therein a multiplicity of distribution holes for introducing the air-fuel mixture toward an air-fuel mixture ejection part is provided with a distribution plate flange part so arranged as to come into direct contact with that portion of the combustion plate flange part which is positioned inside an inner rim of the packing.