A fuel processing apparatus includes a reformer, raw material supply section, moisture supply section, heating section, reforming temperature detection section, shift converter, shift temperature detection section, and control section. When the apparatus is booted, the control section activates the raw material supply section to begin supplying a raw material to the reformer, and activates the heating section to begin supplying heat to the reforming catalyst. Thereafter, when the reforming temperature detection section detects a temperature equal to or greater than a reforming water supply reference temperature, the control section operates the moisture supply section to supply moisture to the reformer, and while the reforming temperature detection section detects a temperature equal to or greater than the reforming water supply reference temperature, determines an amount of moisture to be supplied to the reformer and controls the moisture supply section, based on the temperature detected by the shift temperature detection section.