PROBLEM TO BE SOLVED: To provide a composition comprising a component useful for the prevention of cancer and exhibiting antitumor activity.SOLUTION: The antitumor-activating agent comprises a component extracted from Anninkou (scientific name: Grifola gargal) belonging to the genus Grifola of the Polyporaceae family of the order Aphyllophorales of the Basidiomycetes with water and/or a component extracted with a nonpolar solvent wherein, the antitumor activity is evaluated with at least one kind selected from the group consisting of anti-mutagen activity, anti-urokinase activity and DPPH radical scavenging activity as an indicator.
