To make a fuel reformer, which uses steam reforming reaction and partial oxidation reforming reaction in combination, improved in deformation ratio while the CO concentration is kept equal to or lower than hat in the conventional device and small in size by reducing the load of an evaporator when liquid hydrocarbon is used as fuel.

In this reformer 17 for producing a hydrogen enriched reformed gas by passing a raw fuel gas obtained by evaporating a raw fuel 2 of the mixture of methane gas or a liquid hydrocarbon such as methanol, ethanol, gasoline with water by an evaporator 4 through a reforming catalyst layer and using the steam reforming reaction and the partial oxidation reforming reaction in combination, at least one part of the catalyst layer other than the catalyst layer of a raw fuel gas inlet side is cooled by methane gas or the raw fuel and/or air for the partial oxidation.