Abstract: A welding-operation, liquid crystal, protection mask for protecting the eyes of a human operator from an arc light generated during a welding operation, comprises a liquid crystal protection mask main body adapted to be attached to the face of a human operator; a detecting means disposed in the vicinity of the liquid crystal protection mask main body and capable of detecting an incident arc light generated during the welding operation and thus producing a detection result; a liquid crystal light blocking section that is disposed in a position corresponding to the eyes of a human operator wearing the protection mask with the human face being covered by the protection mask main body and that has a liquid crystal member that is capable of blocking the incident light by instantaneously reducing the light transmittance of the liquid crystal in accordance with the detection result output from the detecting means and by means of a liquid crystal driving power source; and a polarizing plate that is provided in front