In order to develop a novel production process for substitute natural gas (SNG), SiO2-supported metal catalysts effective for methane formation from propane and butanes are investigated under atmospheric pressure. Two reactions, namely, methane formation, C3H8 --> 2 CH4 + C, and decomposi- tion, C3H8 --> 3 C + 4 H-2, took place over the analyzed metal supported catalysts. The highest activity is measured for Ni/SiO2, revealing 100 % conversion and over 90 % selectivity for methanation at 500 degrees C. As far as the activities of other metal supports are concerned, the order is found to be Ni much greater than Co>Fe> Pt>Pd. Butanes show 95 similar to 99 % conversion and 80 % selectivity over Ni/SiO2 at 500 degrees C. Adopting the condition of less than 2,700 h(-1) is found suitable for selective CHI formation. Supplying the feed of C-3 H-8/H-2 = 0.5, only hydrogenolysis of propane takes place over Ni/SiO2 above 250 degrees C, and the conversion reachs 90 % and 100 % at 350 degrees C and 500 degrees C, respectively.