PURPOSE: To lower the resistance value of transparent conductive film, etc. and achieve the improvement in workability by heat-treating the liquid crystal cell having been sealed through heating by using solder glass or the like prior to injection of liquid crystal.

CONSTITUTION: The 1st and 2nd glass plates 3, 4 disposed with transparent electrodes 1, 2 are bonded and sealed by means of low-melting point glass by mutually opposing the transparent electrodes 1, 2 by way of spacers 5a, 5a, 5b at desired spacings to form the liquid crystal cell. If necessary, the transparent conductive films for heating the liquid crystal cell, preferably the films 6, 7 composed of indium oxide or the mixture of tin oxide and indium oxide are beforehand provided onto the other faces of foregoing 1st, 2nd substrates 3, 4. Thence, prior to the injection of liquid crystal into the liquid crystal cell thus formed, this cell is heat-treated in air or in the forming gas composed of mixed gases containing hydrogen, preferably hydrogen and nitrogen. It is desirable that the treating temperature mentioned above is made lower than the heating sealing temperature at the forming of the liquid crystal cell.