PURPOSE: To obtain fluidized bed reforming furnace which is formable compact and is relieved in thermal stress and improved in durability by lessening the heat radiation of reforming pipes.

CONSTITUTION: This fluidized bed reforming furnace 1 is constituted to convert hydrocarbon fuel to gas consisting essentially of hydrogen by supplying the hydrocarbon fuel, such as city gas, and steam to the reforming pipes 10 which are installed to turn back in plural stages horizontally in a fluidizing chamber 2 and are packed internally with reforming catalysts 30 and bringing these reforming pipes 10 into contact with the fluidized bed FB. The both end part of the reforming pipes 10 are supported and mounted at the furnace wall 5 parts and bent pipes 12, 15 of the reforming pipes 10 and a reforming gas header section 20 are positioned and located within the furnace walls 5 of the casing of the reforming furnace body. At least one side end of the reforming pipes 10 are placed and supported on supports 21 within the casing furnace walls.