NOVELTY - Multiple cylindrical steam reforming device for generating reformed gas which carries out steam reforming hydrocarbon fuel, and has hydrogen as a main component, comprises: (a) multiple cylindrical body of same center axis; (b) combustion chamber; (c) exhaust flow path of combustion exhaust gas; (d) pre-heating layer; (e) source gas supply means and water supply means; (f) modification-catalyst layer; (g) shift catalyst layer; and (h) heat exchange acceleration part.    USE - The multiple cylindrical steam reforming device is useful for generating reformed gas (claimed). It can also be used as a fuel treating apparatus of a polymer electrolyte fuel cell (PEFC).    ADVANTAGE - Using the device, size reduction of shortening of boundary part length and the whole apparatus is attained.    DETAILED DESCRIPTION - Multiple cylindrical steam reforming device for generating reformed gas which carries out steam reforming hydrocarbon fuel, and has hydrogen as a main component, comprises: (a) multiple cylindrical body of same center axis; (b) combustion chamber which burns fuel gas to cylindrical body inner side center part, and produces combustion exhaust gas to it; (c) exhaust flow path of combustion exhaust gas formed along the inner side of first partition; (d) pre-heating layer which is formed in interval of a first partition and second partition upper stage part, and heat exchanges any one or both of the source gas supplied or water with combustion exhaust gas through a first partition; (e) source gas supply means and water supply means; (f) modification-catalyst layer which reforms the mixed gas which was formed in the interval of a first partition and a second partition lower-stage part, and passed the pre-heating layer to hydrogen-containing-gas; (g) shift catalyst layer which transforms the reformed gas which was formed in the interval of second partition upper stage part and third partition middle step part, and came out of the modification-catalyst layer; and (h) heat exchange acceleration part formed in the boundary part of a pre-heating layer and modification-catalyst layer, where the heat exchange acceleration part comprises first heat-exchange chamber and second heat-exchange chamber which are divided by the partition plate provided with the communicating hole, a first heat-exchange chamber is comprised so that it may form in the interval of this partition plate and second partition and the mixed gas which flows in from pre-heating layer can heat-exchange with a shift catalyst layer through a second partition, it comprised so that a second heat-exchange chamber might be formed in the interval of a first partition and this partition plate and the mixed gas which flows in through a communicating hole from a first heat-exchange chamber could heat-exchange with combustion exhaust gas through a first partition.