NOVELTY - Oxide of cobalt, vanadium and transition metal supported on inactive porous support is new.    USE - For preparing carbon nanotube used as electro-conductive and strength enhanced polymer composite material, support material of fuel battery catalyst, support material of organic process catalyst, storage material for methane and hydrogen gas, electrode material of lithium secondary battery, conductive material of lithium secondary battery, electrode material for high double layer capacitor, emitting material for display and membrane material (claimed).    ADVANTAGE - The catalyst enables to produce the carbon nanotube having 5-30 nm of diameter and 100-10000 of aspect ratio in a high catalytic yield and in a short reaction time. The catalytic yield can be enhanced more than 3 times compared to a formerly developed catalyst composition.    DETAILED DESCRIPTION - A catalyst comprising oxide of cobalt, vanadium and transition metal supported on inactive porous support, of formula (CoxVy(M1)z)p(M2)q is new.    Co=catalytic metal of cobalt, its oxide or its derivative;    V=catalytic metal of vanadium, its oxide or its derivative;    M1=at least one catalytic transition metal selected from Al, Fe, Ni, W, Cr, Mn, Sn, Cu, Y, Zr, Ti, Mo or Si, its oxide or its derivative;    M2=inactive porous support selected from Mg or Si, its oxide or its derivative;    p and q=0.05-0.95;or    p+q=1;    x=0.03-0.75;    y=0.02-0.75;    z=0.01-0.95;or    x+y+z=1.    INDEPENDENT CLAIMS are included for the following:    (1) preparing (m1) the catalyst;    (2) preparing (m2) carbon nanotube involving: i) preparing a catalyst composition for the synthesis of carbon nanotube; ii) supplying at least one carbon source selected from saturated or unsaturated 1-4C hydrocarbon to the reactor at 500-800 degrees C; and iii) growing and synthesizing carbon nanotube by decomposition of supplied carbon source on the surface of a catalyst composition according to chemical vapor deposition method.