To provide a method for inactivating a virus required for a treating means in order to make a patient suffering from viral infection prolong the life.

This method for inactivating the virus having an envelope such as a retrovirus, e.g. HIV, HBC, HCV, HDV, HGV, HTLV-1, HTLV-2 and PERV or other viruses comprises using a silicone emulsion prepared by mixing a silicone resin with an emulsifying agent such as a sorbitan ester of a fatty acid, a glycerol ester of the fatty acid, a sucrose ester of the fatty acid and sodium cellulose glycolate and emulsifying the silicone resin. The method for inactivating the retrovirus such as the HIV present in blood or a body or other viruses comprises carrying out subcutaneous injection, injection into blood or oral administration of a trace amount of the silicone emulsion prepared by mixing a dimethylsilicone oil compound obtained by formulating a dimethylsilicone oil having a dimethylpolysiloxane structure with a special dispersing agent with the emulsifying agent and emulsifying the dimethylsilicone oil compound into a patient suffering from the viral infection.