PURPOSE: To surely inject an extraneous substance into a cell while suppressing the damage on the cell using a micro-injection apparatus for injecting a substance into a biotissue or cell.

CONSTITUTION: A plate 10 holding regularly arranged cells is placed on a micromanipulation stage and a needle 20 fixed to a fine-adjustment positioning apparatus 13 is approached to a cell 11 and slowly inserted into the cell while observing the cell with a stereo-microscope 14. A substance to be injected into the cell is preparatorily applied to the tip of the needle by electrodeposition. A needle 22 different from the needle coated with the injection substance is inserted into the cell at a side opposite to the coated needle and a voltage is applied between the needles with a power source 15. The injection substance fixed to the needle by electrodeposition is actively released into the cell by this process.