To obtain a pharmaceutical preparation having high antiviral properties with scarcely any adverse effects and further having sufficient prophylactic and recovering effects on especially hepatitis C virus(HCV) infectious diseases without effective treating means.

This antiviral pharmaceutical preparation for prophylaxis and treatment of viral infectious diseases comprises gomisin A or its derivative compound as a crude drug. The prophylactic and therapeutic method for the viral infectious diseases using the pharmaceutical preparation is obtained. Since not only remarkable effects on the prophylaxis and treatment of HCV infectious diseases can be exhibited but also the morbid state of hepatitis can be improved, the preparation can efficiently be used for treating hepatitis due to the HCV. Even an extract essence of Schizandrae Fructus containing the gomisin A can be used for the prophylaxis and treatment of the hepatitis and viral infectious diseases.