PURPOSE: To make it possible to move a microplate together with a stage relatively to a hood and electrode without contamination of various germs, by providing the hood covering the microplate and electrode independent of a microscopic stage.

CONSTITUTION: A cell suspension is put in many wells 6 in a microplate 4 and placed on a stage 12 of a microscope. An optical axis is adjusted to one well 6 thereof and an electrode plate 40 is inserted thereinto while observing the interior of the well. A voltage is then applied to carry out cell fusion or gene introduction. An apparatus therefor is constituted as follows. A hood 26 covering the plate 4 with a margin is fixed to the body of the microscope using a joining metal fixture 34. Freely rotatable wheels 28 are provided at the leg parts in the skirt part of the hood 26. The resultant hood 26 is then brought into contact with the stage 12. A hole is made at a position corresponding to the optical axis of the hood 26 and an electrode block 30 is inserted therein and connected to the hood 26 with bellows 32 so as to be vertically movable.