An object of the present invention is to provide an anti-human norovirus agent which can inhibit infection with and proliferation of human norovirus. The present inventors have found that the object can be attained through provision of an anti-human norovirus agent comprising, as an active ingredient, a fucose analog having an inhibitory action on glycosylation by fucosyltransferase (FUT). Examples of the active ingredient include a fucose analog represented by formula (III) or (IV) or a salt thereof.

[In the formulas, each of formula (III) and formula (IV) represents an α-anomer or a β-anomer; each of R 1 , R 3 , and R 4 is -OH or -OAc; R 2 is a halogen atom, -OH, or -OAc; and R 5 is -CH 3 , -C=CH, -C≡CCH 3 , or -CH 2 C≡CH.]