Disclosed is a method for introducing a foreign substance (3) into a cell (1) having a cell wall. The method comprises the steps of: providing a carbon nanotube (2) carrying at least one enzyme capable of decomposing a cell wall; supplying the carbon nanotube (2) and the foreign substance (3) into a treatment solution containing the cell (1); decomposing the cell wall of the cell (1) by the action of the enzyme carried on the carbon nanotube (2) upon the contact of the carbon nanotube (2) with the cell (1); and introducing the foreign substance (3) into the cell (1) through a site decomposed with the enzyme on the cell wall.