A carbon nanotube forming method including providing a target substrate to be processed, a catalytic metal layer being formed on a surface of the target substrate; producing catalytic fine metal particles whose surfaces are oxidized by action of an oxygen plasma on the catalytic metal layer at a temperature T1; and activating the oxidized surfaces of the catalytic fine metal particles by reducing the oxidized surfaces of the catalytic fine metal particles by action of a hydrogen plasma on the catalytic fine metal particles at a temperature T2 higher than the temperature T1. The method further includes growing a carbon nanotube on the activated catalytic fine metal particles by thermal CVD at a temperature T3.