NOVELTY - A modification part (1) converts hot raw material gas containing steam and dimethyl ether (DME) in vapor hot spot (3), to form reformed gas using ether hydration and methanol modification catalysts. The exhaust heat obtained by hot combustion of the catalyst in combustion part (2) is sent to a heat recovery part (4) so as to use it as heat source for vapor hot spot and water evaporation part. DETAILED DESCRIPTION - The modifier has an evaporation part (8) to evaporate DME and a water heat part (7) to heat water required to perform the conversion of DME to hydrogen. A water evaporation part (5) evaporates water heated in the water heat part. Steam obtained in the water evaporation part and DME obtained in the evaporation part are supplied as raw material to a vapor hot spot (3) and heated. A modification part (1) is provided to carry out conversion of hot raw material gas to reformed gas using ether hydration catalyst and methanol modification catalyst. A combustion part (2) supplies heat to the modification part and an oxidation part (6) reduces carbon monoxide in the reformed gas by the oxidation of the catalyst. The exhaust heat obtained by hot combustion of the catalyst is sent to a heat recovery part (4) so as to use it as heat source for vapor hot spot and water evaporation part. A stripping section (9) provided adjacent to the evaporation part recovers methanol of unreacted DME and reaction intermediate product. An INDEPENDENT CLAIM is also included for the DME fuel modification method which involves using the heat of vaporisation of DME in the evaporation part, to reduce the process temperature during recovery of methanol.    USE -   For portable fuel batteries used in general power supply and electric vehicles.    ADVANTAGE -   The formation rate of high quality DME is improved. The unreacted raw material is effectively recovered and reduction of fuel loss is attained. The size of the apparatus is minimised and conversion efficiency of DME to hydrogen is increased. Recycling of raw material is enabled and temperature distribution in the modification part is made uniform. DESCRIPTION OF DRAWING(S) - The figure shows the block diagram of fuel modifier. (1) Modification part; ; (2) Combustion part; ; (3) Vapor hot spot; ; (4) Heat recovery part; ; (5) Water evaporation part; ; (6) CO oxidation part; ; (7) Water heat part; ; (8) Evaporation part; ; (9) Stripping section.