To provide a protective face HG for always clearly and visually observing a welding part, even when variation in intensities of the arc light is caused due to a factor which cannot be discriminated by a waveform of a welding current or welding voltage.

The protective face HG is mounted with a light shielding panel GP for protecting eyes of a welding operator from the arc light, and comprises: an illuminance sensor SD for measuring illuminance of the arc light passed through the light shielding panel GP; and a transmissivity control part GC for controlling light transmissivity of the light shielding panel GP so that a measured value Sd of the illuminance becomes equal to a predetermined illuminance set value. Even when intensities of the arc light are varied by the factor that cannot discriminate the change by the waveform of the welding current or the welding voltage such as a welding attitude, a welding advance position and a distance up to the protection face from an arc generation part, since the illuminance after passing through the light shielding panel GP can be kept to a desired value, the welding part can be always clearly and visually observed.