Catalytic decomposition of methane into carbon and hydrogen was examined on Ni-based catalysts. The Ni catalyst supported on zirconia that was synthesized by the glycothermal method showed the highest carbon yield. TEM observation revealed that multi-walled carbon nanotubes with an average diameter of similar to30 nm were formed on this catalyst. Effects of the modification of the Ni/zirconia catalyst with other metal elements were also examined. The products formed on the Ni-Cu catalysts contained carbon filaments with the graphite sheets oriented at a certain angle with respect to the growth axis of the filament. The carbon nanotubes formed on the Ni-Co, Ni-Fe and Ni-Mo catalysts had the narrow distributions of tube diameter as compared with those formed on the Ni catalysts. Although the Ni-Mn catalyst exhibited a very low yield of carbon nanotubes, they had smaller populations of bends than the carbon nanotubes formed on the other Ni-based catalysts.