The present invention relates to a monoclonal antibody or an antibody fragment thereof, which binds to the extracellular region of human Trop-2 with high affinity and exhibits high ADCC activity and high antitumor activity a hybridoma which produces the antibody a DNA which encodes the antibody a vector which comprises the DNA a transformant obtainable by introducing the vector a process for producing an antibody or an antibody fragment thereof using the hybridoma or the transformant and a therapeutic agent or a diagnostic agent using the antibody fragment thereof.
