A compound including a polymer is represented by general formula (1): L-Y-A  (1) wherein, A is a single-chain antibody moiety, which is a polypeptide including an antigen-binding site, L is a linker moiety, which is a polypeptide including a protease cleavage site, Y is a peptide moiety, which includes 0 or more amino acids connecting the linker moiety L with the single-chain antibody moiety A, and the linker moiety L binds to an N terminus of the peptide moiety Y or an N terminus of the single-chain antibody moiety A.