A fuel reforming apparatus for a polymer electrolyte membrane fuel cell, characterized in that each of a reformer, a carbon monoxide converter, a carbon monoxide selective oxidizing reactor, a cooling device for cooling the inlet port of the carbon monoxide converter, and a cooling device for cooling the inlet gas of the carbon monoxide selective oxidizing reactor is formed cylindrical, the reformer is arranged in the center, the carbon monoxide converter is arranged on the outer circumferential portion of the reformer, and the carbon monoxide selective oxidizing reactor is arranged on the outer circumferential portion of the carbon monoxide converter so as to make reformer, transformer and reactor integral.