A fuel reforming apparatus in constructed with a main body including a first pipe and a second pipe disposed in the first pipe and a heat source installed in the second pipe and adapted to generate thermal energy in the second pipe. A reforming reaction unit is formed by filling a reforming catalyst in a space defined between the first and second pipes and is adapted to generate a reformed gas containing hydrogen through a reforming reaction of the fuel. A housing encloses the main body and allows a combustion gas generated from the heat source to flow along an outer circumference of the reforming reaction unit.