In a reforming apparatus, for use in a fuel cell, for reforming a raw fuel into a hydrogen-rich reformed gas, a reformer generates the reformed gas from the raw fuel. A shift reactor reduces carbon monoxide contained in the reformed gas through a shift reaction. A selective oxidation unit reduces the carbon monoxide contained in the reformed gas that has passed through the shift reactor by performing selective oxidation on the carbon monoxide. A reforming reaction tube houses linearly the reformer, the shift reactor and the selective oxidation unit in this order.