An anti-8-OHdG antibody and an antibody fragment thereof, with which 8-hydroxy-2′-deoxyguanosine (8-OHdG) in a specimen, particularly urine, can be accurately analyzed, and a measuring method capable of measuring 8-OHdG in a specimen, particularly urine, with high sensitivity are provided. An anti-8-OHdG antibody or an antibody fragment thereof which reacts specifically with 8-OHdG and substantially does not react with urea; the antibody or antibody fragment thereof in which the complementarity-determining regions of the variable regions of heavy and light chains are specific amino acid sequences; and a measuring method for 8-OHdG in a specimen using the antibody or antibody fragment thereof are disclosed.