The present invention relates to an antibody specifically binding to glypican 3 (GPC3), a nucleic acid encoding the antibody, a vector and a host cell containing the nucleic acid, a method of preparing the antibody, and a pharmaceutical composition for treating cancer or tumor, containing the antibody as an active ingredient. The antibody specifically binding to glypican 3 according to the present invention may be effectively used to treat cancer or tumor, particularly, hepatocellular carcinoma due to high affinity and specificity to glypican 3.