It is an object of the present invention to provide an anti-GPR20 antibody that can be used in the detection of GPR20, a reagent for GPR20 detection comprising the antibody, a reagent for diagnosis or a composition for testing of a disease related to the expression of GPR20, etc. The present invention provides an antibody specifically binding to a peptide comprising the amino acid sequence at amino acid positions 1 to 48 in SEQ ID NO: 1, or an antigen-binding fragment of the antibody, a chimeric antibody of the antibody, a rabbit type antibody of the antibody, etc. The present invention also provides a composition comprising the antibody, etc.