Abstract: An ADAMTS13 mutant protein having an improved escaping rate against an autoantibody and a composition that is suitable for preventing or treating thrombotic diseases are disclosed. By efficiently avoiding autoantibodies known to have high binding affinity to the main domain of ADAMTS13, the ADAMTS13 variant protein of the present invention can be used as an effective therapeutic composition for various thrombotic diseases, such as TTP (thrombotic thrombocytopenic purpura), in which the presence of such autoantibodies is the main etiology, and can stably maintain the biological activity thereof when administered into a body. In addition, a newly identified site within ADAMTS13, which is recognized by an autoantibody can be used in screening novel ADAMTS13 variants having an improved autoantibody escaping rate by applying a combination of various mutations within the corresponding site.