PROBLEM TO BE SOLVED: To provide an antiviral agent utilizing a plant belonging to family Poaceae, genus Phyllostachys, specifically to provide an antiviral agent against influenza virus.SOLUTION: The antiviral agent includes the antiviral substance contained in the plant belong to genus Phyllostachys as an effective component, and the agent is specifically effective to control influenza virus infection. The effective component is the antiviral substance included in the whole plant body or parts of the plant body such as the leaves and stems. They can be used as it is, but preferably used after pulverization or crushing by using a pulverizer or a crusher. The antiviral agent can be obtained by conventional methods such as solvent extraction with water (hot water) or alcohol (ethanol etc.) or compression, but a preferable method is distillation carried out by heating the plant of genus Phyllostachys under diminished pressure.
