An anti-equol antibody composition, containing an anti-equol antibody or antibody fragment thereof containing, as an immunoglobulin heavy chain variable region, hypervariable regions CDR1, CDR2, and CDR3 respectively including amino acid sequences represented by SEQ ID NO: 1-3, and as an immunoglobulin light chain variable region, hypervariable regions CDR1′, CDR2′, and CDR3′ respectively including amino acid sequences represented by SEQ ID NO: 4-6; and an anti-equol antibody or antibody fragment thereof containing, as an immunoglobulin heavy chain variable region, hypervariable regions CDR1, CDR2, and CDR3 respectively including amino acid sequences represented by SEQ ID NO: 1-3, and as an immunoglobulin light chain variable region, hypervariable regions CDR1′, CDR2′, and CDR3′ respectively including amino acid sequences represented by SEQ ID NO: 7-9.