A fuel reforming apparatus including reaction substrates is provided. The reaction substrates of the present invention is made of stainless steel, nickel steel, or chromium steel. Each of the reaction substrates has a channel formed on the surface of the reaction substrate. Reactant for oxidation reaction or for fuel reforming reaction flow through the channel. A catalyst containing layer is formed on the surface of the channel by directly oxidizing the surface of the channel. Therefore, the catalyst containing layer is formed with oxidized steel. A catalyst layer is formed on the catalyst containing layer. A pair of substrates can be laminated to make one substrate a thermal source unit and another a reforming reaction unit.