PURPOSE: To permit easy and satisfactory replacement of a liquid crystal by immersing one aperture into a fluorine org. solvent having high volatility and sucking the liquid crystal from the other aperture by vacuum pump thereby substituting the inside of a cell with the solvent.

CONSTITUTION: One aperture 11A is first immersed into the fluorine org. solvent 22' which has high volatility and does not affect orientation, then the other aperture 11B is connected via a pipe 23 to the vacuum pump in the case of replacing the liquid crystal. The liquid crystal in the cell 10 is sucked out by the suction force of the vacuum pump and the solvent 22' in the vessel is sucked into the cell 10 to substitute the cell inside with the solvent. The aperture 11A is detached from the solvent in the vessel after the substn. and the suction by the vacuum pump is continued to suck out the solvent out of the cell 10. Since the solvent 22' has the high volatility, the solvent in the cell is thoroughly sucked to the outside of the cell 10. The aperture 11A of the cell 10 is thereafter immersed into the defoamed liquid crystal and the liquid crystal is sucked by the vacuum pump, then the liquid crystal is reinjected into the cell.