The present invention is directed to a fuel reformer device that produces a hydrogen rich gas from a hydrocarbon and steam. A reformer unit receives a supply of a crude fuel gas containing air through a second supply conduit. The crude fuel gas is subjected to a steam reforming reaction and an oxidation reaction proceeding inside the reformer unit. A resulting hydrogen rich gaseous fuel is discharged. The reformer unit includes an upper stream reaction unit and a lower stream reaction unit. The reformer unit is designed to enable the heat generated on the upstream side to be effectively transmitted to the lower stream side. This arrangement thus effectively prevents an excessive temperature rise on the upstream side.
