To provide a compact low CO reformed gas production unit and a low CO reformed gas production system where hydrocarbon-based fuel such as gasoline and light oil can swiftly and sufficiently be reformed even under a lower temperature condition, the by-production of CO hardly occurs, and gaseous hydrogen is not subjected to nitrogen dilution, and to provide a fuel reform system for a fuel battery.

In the low CO reformed gas production unit, a hydrocarbon-based fuel feeding means and a water feeding means feed fuel and water into a supercritical reforming reactor, and the fuel and the supercritical water or sub-critical water are reacted under a reforming catalyst. In the fuel reform system for a fuel battery, the downstream side of the low CO reformed gas production unit is provided with a moisture removal means, a pressure recovery means, a fuel battery, a moisture recovery means and a waste hydrogen combustor, low CO reformed gas and air are fed to the fuel battery, the supercritical reforming reactor is heated with the combustion heat of the low CO reformed gas exhausted from the fuel battery, and moisture exhausted from the fuel battery and the waste hydrogen combustor is reutilized.