A fuel reformer for producing a steam reforming reaction between fuel and water on a reforming catalyst includes a fuel injection part that injects and supplies fuel into the reforming catalyst, and an injection control part that controls an injection amount of fuel by the fuel injection part. The injection control part controls the injection amount in order that a temperature of the reforming catalyst is not lower than a preset given temperature. The fuel reformer further includes a temperature obtaining part that measures or estimates the temperature of the reforming catalyst, and a target value calculation part that calculates a target value of the injection amount, such that the temperature of the reforming catalyst after fuel is injected by the fuel injection part is equal to or higher than the given temperature. The fuel injection part is controlled such that the injection amount coincides with the target value.