The present invention relates to an anti-MRS monoclonal antibody and, more specifically, to an antibody or a fragment thereof characterized by specifically binding to a fragment represented by amino acid 861-900 of a human-derived methionyl-tRNA synthetase (MRS) protein set forth in SEQ ID NO:1, a method for producing the same, and a composition for diagnosing cancer comprising the same. The antibody or the fragment thereof of the present invention specifically binds to the human-derived MRS, and has no cross-reactivity with other proteins comprising the same ARS family. Therefore, as MRS detection is possible, the antibody or a fragment thereof can be effectively used for diagnosing MRS-related cancer.