Viruses, and particularly RNA viruses, have high mutation rates. Hence, antiviral agents that have been developed to date targeting protease or reverse transcriptase of viruses have quickly lost their effectiveness and resistant viruses have emerged. Also, in recent years, viral diseases caused by various new viruses such as SARS, avian influenza, and the hepatitis C have become social menaces. Therefore, the development of a novel antiviral agent that can cope with a virus resistant to an existing drug or a new virus and has a wide range of applications has been demanded. The present invention provides a novel anti-RNA viral agent and a method for use thereof. The present invention further provides an anti-RNA viral agent that is also effective against a new virus or a drug-resistant virus, and a method for use thereof.