An anti-human-norovirus GII antibody which responds to substantially all genotypes of the human noroviruses belonging to GII and which can comprehensively detect such human noroviruses GII. The anti-human-norovirus GII antibody that binds to at least one of epitopes which are contained in amino acid regions represented by the following formulas (1) and (2): P-X1-X2-P-G-E  (1) (SEQ ID NO: 2) X3-X4-X5-F-Y-X6-L-X7-P-X8  (2) (SEQ ID NO: 3) (wherein, X1 represents L, V, N, T, S, M, or R; X2 represents F, Y, or M; X3 represents V or G; X4 represents N or S; X5 represents Q, P, or S; X6 represents S, T, or I; X7 represents A or S; and X8 represents M or V), and of an epitope formed of amino acid 483 of the amino acid sequence represented by SEQ ID NO: 1, or an epitope formed of an amino acid corresponding to amino acid 483, the regions and the amino acids being present in the P domain of a capsid structural protein of a human norovirus GII.