Provided is a novel anti-Glypican-1 antibody and a method for using the same. Provided is an anti-Glypican-1 antibody having an intracellular migration activity which has never been observed in conventional anti-Glypican-1 antibodies. By taking advantage of the intracellular migration activity of the antibody according to the present invention, the present invention is usable for various therapeutic purposes beyond the scope of the conventional assumption. Also provided is a composition for preventing or treating Glypican-1 positive cancer, said composition comprising a complex of a substance capable of binding to Glypican-1 (for example, an anti-Glypican-1 antibody) with a drug having a cytotoxic activity.
