NOVELTY - A catalyst-supporting carbon nanotube is prepared. An ionomer solution is prepared, and the nanotube is contacted with ionomer solution (4) and coated with the ionomer. The coated nanotube is dried. At least one iteration of a sequential process including the steps from ionomer coating to drying is carried out. After ionomer coating and before drying, the portion of the ionomer which has adhered unevenly in a thickness direction of a layer formed from ionomer-coated catalyst-supporting carbon nanotube (5) is removed to a relatively greater degree than on other sites of nanotube.    USE - Manufacture of ionomer-coated catalyst support carbon nanotube for fuel cell.    ADVANTAGE - The catalyst-supporting carbon nanotube which is uniformly coated with ionomer from the base to the end portion of the carbon nanotube, is manufactured. Since the precipitation towards ionomer edge portion is reduced, the contacting time of ionomer solution and carbon nanotube is reduced.    DETAILED DESCRIPTION - A catalyst-supporting carbon nanotube which is oriented approximately perpendicular (20) to the direction of the plane of substrate, is prepared. An ionomer solution is prepared, and the catalyst-supporting carbon nanotube is contacted with ionomer solution and coated with the ionomer. The coated nanotube is dried. At least one iteration of a sequential process including the steps from the ionomer coating step to the drying step is carried out. After the ionomer coating and before drying, preferentially the portion of the ionomer which has adhered unevenly in a thickness direction of a layer formed from the ionomer-coated catalyst-supporting carbon nanotube that has adhered on the end portion of the carbon nanotube is removed to a relatively greater degree than on other sites of the carbon nanotube.    DESCRIPTION OF DRAWING(S) - The drawing shows the cross-sectional view of ionomer-coated catalyst support carbon nanotube.    Substrate (1)    Carbon nanotube (2)    Catalyst (3)    Ionomer solution (4)    Ionomer with excess carbon nanotube edge portion (4a)    Ionomer-coated catalyst support carbon nanotube (5)    Perpendicular direction (20)