Evaporation chamber for depositing a protective film on a surface, where a dielectric layer is formed, of front substrate, front substrate is formed a display electrode and the dielectric layer thereon; transporting unit for transporting front substrate into evaporation chamber; gas introducing units for introducing gas containing H2O into evaporation chamber; and partial pressure detecting unit for measuring a certain partial pressure of gas within evaporation chamber, extending from the center of deposition space of evaporation chamber to the downstream of transport direction of front substrate are provided. Gas containing H2O is introduced from gas introducing units such that the partial pressure of gas is controlled in the partial pressure detecting unit.