The invention relates to an antibody which binds to chondroitin sulfate proteoglycan 5 (CSPG5) or an antibody fragment thereof, a hybridoma which produces the antibody or the antibody fragment thereof, a nucleic acid comprising a nucleotide sequence encoding the antibody or the antibody fragment thereof, a transformant cell comprising a vector comprising the nucleic acid, a method for producing the antibody or the antibody fragment thereof, a composition comprising the antibody or the antibody fragment thereof, and a method for detecting or measuring an antigen present in the brain, a method for diagnosing or treating a brain disease, a method for enhancing the property of accumulating in a brain of an antibody, and a method for increasing the amount of an antibody in the brain, each of which using the antibody or the antibody fragment thereof, and the like.