The present invention is an antibody including an amino acid sequence, wherein the amino acid sequence includes, in an N- to C-direction, the following structural domains: N-FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4-C wherein FR denotes a framework region amino acid sequence and CDR denotes a complementary determining region amino acid sequence; the CDR1 includes an amino acid sequence represented by SEQ ID NO: 1; the CDR2 includes an amino acid sequence represented by SEQ ID NO: 2; the CDR3 includes an amino acid sequence represented by SEQ ID NO: 3; and the antibody is capable of binding to an intranuclear protein of an influenza virus.