A multiple antigen-binding molecule fusion molecule containing a multiple antigen-binding molecule (α) having an immune cell antigen-binding region and a cancer antigen-binding region, a cancer tissue-specific protease-cleavable linker (β), and a masking molecule (γ) containing a polypeptide having the amino acid sequence QDGNE, in which the multiple antigen-binding molecule (α) and the masking molecule (γ) are linked via the cancer tissue-specific protease-cleavable linker (β).