NOVELTY - Fuel reformer comprises reformer (1), oxidizing agent supply device, reaction heat variation detection unit, fuel flow rate calculation unit and oxidizing agent flow rate calculation unit. An oxidizing agent flow rate correction unit corrects calculated flow rate of oxidizing agent such that temperature of portion of reformer is set to target temperature based on estimated heat change.    USE - For forming reformed gas containing hydrogen.    ADVANTAGE - The flow rate of oxidizing agent is corrected such that the temperature of the reformer is set to predetermined value hence the non-linear heat change at the inlet of oxidizing agent within the reformer is adjusted. Hence the reformer can be maintained to target temperature. By managing the temperature in the reformer, the reduction of activity of the catalyst, inside the reformer is eliminated. The temperature of the reformer can be maintained to the target value immediately after change in the temperature.    DETAILED DESCRIPTION - A fuel reformer comprises reformer for carrying out oxidizing reaction of fuel and oxidizing agent to form reformed gas containing hydrogen, accompanied by heat, and oxidizing agent supply device for supplying oxygen to the reformer. Reaction heat variation detection unit for detecting variation of reaction heat amount within reformer, fuel flow rate calculation unit for calculating flow rate of fuel supplied to reformer and oxidizing agent flow rate calculation unit for calculating flow rate of oxidizing agent supplied to the reformer based on fuel flow rate are provided. An oxidizing agent flow rate correction unit corrects the target flow rate of oxidizing agent calculated by oxidizing agent flow rate calculation unit such that temperature of the portion of reformer is set to target temperature based on variation in heat estimated by the reaction heat variation detection unit.    DESCRIPTION OF DRAWING(S) - The drawing shows block diagram of fuel reformer. (The drawing includes non-English language text).    reformer (1)