To reduce the heat loss of a radiation heating type premixing burner and, to effectively burn organic matters contained in the exhaust gas of the burner by arranging an air-permeable porous material in the burning space of the burner and making the exhaust gas to pass through the porous material.

Surface combustion burners 12 are arranged inside a cylindrical main body 11 and an air-permeable porous material 13 is arranged in the inside space of the main body 11. An exhaust gas containing organic matters are sucked into the main body 11 through one opening of the main body 11 and the exhaust gas after burning is discharged from the other opening. In addition, dispersing plates 16 are interposed between the side wall of the main body 11 and burners 12 in a state where the plates 16 surround the burners 12 and a ceramic foam is applied to the porous material 13.