High intensity combustion and low intensity combustion are carried out together, to stabilize flames and to hold down the emission of carbon monoxide. An air-fuel mixture outlet member (back plate) that includes a single or a plurality of outlet(s) (air-fuel mixture outlet(s)) out of which an air-fuel mixture (GA) flows is included, and a metal fiber knitting body (metal knit) that covers the air-fuel mixture outlet member is included. Therefore, the air-fuel mixture, which is made to flow out of the outlet(s), passes through the metal fiber knitting body (metal knit) and is combusted, a flame of low intensity is generated together with a flame of high intensity by combustion of the air-fuel mixture, and the flame of low intensity holds the flame of high intensity.