NOVELTY - The fuel burner comprises an air supply hole connected to a firing rod (121) of an ignition plug (120) and protruded to an end and a fuel supply port in which fuel is supplied to a burner body (110). A first tube (130) forms a path, which is combined in an end of the burner body, where the air and the fuel are flown toward an exterior of the firing rod in the path. A second tube (140) forms another path in which air is flown towards an exterior of the first tube. The air flowed through the air supply hole and the fuel flowed through the fuel supply port are mixed in the first tube.    USE - The fuel burner is useful in a fuel cell system (claimed).    ADVANTAGE - The burner prevents spontaneous ignition and backfire, and has improved durability.    DETAILED DESCRIPTION - The fuel burner comprises an air supply hole connected to a firing rod (121) of an ignition plug (120) and protruded to an end and a fuel supply port in which fuel is supplied to a burner body (110). A first tube (130) forms a path, which is combined in an end of the burner body, where the air and the fuel are flown toward an exterior of the firing rod in the path. A second tube (140) forms another path in which air is flown towards an exterior of the first tube. The air flowed through the air supply hole and the fuel flowed through the fuel supply port are mixed in the first tube. A gap maintenance member uniformly maintains a gap between exteriors of the first tube and the second tube and is equipped between an outer leading end of the first tube and a leading end of the second tube. Groove portions discharge the air in the second tube between an outer surface leading end of the first tube and an inner surface leading end of the second tube and penetrate from an end part to another end part. An ash generator is connected to the leading end of the first tube and the firing rod. An outer periphery of the gap maintenance member closely adheres an inner surface of the second tube. The gap maintenance member is formed in a ring shape. An inner periphery of the gap maintenance member closely adheres the exterior of the first tube.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic cross-sectional view of a fuel burner of a fuel cell system.    Burner body (110)    Ignition plug (120)    Firing rod (121)    First tube (130)    Second tube. (140)