To provide a method for inactivating virus by the dry heating of fibrinogen having a fear of virus contamination in which a denaturation rate and/or a devitalization rate of the fibrinogen by heating are/is low, and the solubility and the dissolved condition of the obtained fibrinogen are satisfactory. ウイルス夾雑の危惧のあるフィブリノゲンの乾燥加熱によるウイルス不活化法において、加熱によるフィブリノゲンの変性、失活率が低く、且つ得られたフィブリノゲンの溶解性や溶状が良好であるウイルス不活化法の提供。 - 特許庁