NOVELTY - The reformer has hollow tubular portion (70) that is defined with reforming chamber (76) filled with reforming catalyst (75). A supply chamber (78) arranged upstream of reforming chamber, uniformly supplies raw fuel to raw fuel passage (74) set in the reforming chamber. A discharge chamber (80) arranged downstream of reforming chamber, uniformly discharges reformed raw fuel from fuel passage. The passage has reverser (74a) to reverse fuel flow direction. The fuel passage has cross-sectional area that is smaller in downstream portion than that in upstream portion.    USE - Reformer is used for fuel cell e.g. solid oxide fuel cell (both claimed). Can also be used for reforming hydrocarbon containing raw fuel supplied to solid oxide fuel cell module used in stationary fuel cell system and vehicle-mounted fuel cell system, liquefied natural gas (LNG), liquefied petroleum gas (LPG), ethanol, methanol, petrol, kerosene and biofuel supplied to molten carbonate fuel cell (MFC) module, phosphoric acid fuel cell (PAFC) module, hydrogen membrane fuel cell (HMFC) module and solid polymer electrolyte fuel cell (PEFC) module.    ADVANTAGE - Since raw fuel passage is set with reversers for reversing the fuel flow direction, overall length of the reformer can be reduced and raw fuel passage can be elongated effectively. Since cross-sectional area of the raw fuel passage is smaller in its downstream portion than in its upstream portion, raw fuel flows through entire region of the raw fuel passage at minimum flow velocity. Hence raw fuel is evenly distributed in raw fuel passage while ensuring contact with reforming catalyst over a long period of time even in wide operating range so as to improve reforming capability of the reformer. Hence reformer which is simple in structure and small in size, is capable of maintaining desired reforming efficiency and reforming capability in wide operating range, is highly durable, and is capable of supplying reformed raw fuel stably.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of the reformer.    Hollow tubular portion (70)    Raw fuel passage (74)    Reverser (74a)    Reforming catalyst (75)    Reforming chamber (76)    Supply chamber (78)    Discharge chamber (80)