The present invention relates to an injenane-type diterpene compound derived from Euphorbia kansui Liou, and a pharmaceutical composition for treating or preventing viral infectious diseases, a health functional food for preventing or ameliorating viral infectious diseases and a composition for enhancing the production of interferon-gamma, which comprise the injenane-type diterpene compound. Furthermore, the present invention relates to a method for preventing or treating viral infectious diseases including administering the composition to a subject having a viral infectious disease occurrence or a risk thereof with a therapeutically effective dose.
