A multiple antigen-binding molecule fusion molecule comprising: a multiple antigen-binding molecule (α) which comprises an immune cell antigen-binding region which recognizes an antigen that comprises a polypeptide consisting of the amino acid sequence QDGNE (SEQ ID NO: 15) and a cancer antigen-binding region which recognizes a cancer antigen; a cancer tissue-specific protease-cleavable linker (β) which comprises a polypeptide consisting of a target sequence of a cancer tissue-specific protease; and a masking molecule (γ) which comprises a polypeptide consisting of the amino acid sequence QDGNE (SEQ ID NO: 15); wherein the multiple antigen-binding molecule (α) and the masking molecule (γ) are linked via the cancer tissue-specific protease-cleavable linker (β), wherein the multiple antigen-binding molecule (α) is an antibody or an antibody fragment comprising at least two Fv regions, and the cancer antigen-binding region and the immune cell antigen-binding region are formed by different Fv regions, wherein the cancer tissue-specific protease-cleavable linker (β) is fused to a heavy chain N-terminus or a light chain N-terminus of the Fv region that forms the immune cell antigen-binding region, wherein the cancer tissue-specific protease-cleavable linker (β) and the masking molecule (γ) form a linear fusion polypeptide, and wherein the number of amino acids in the fusion polypeptide is eleven or more to 65 or less when the cancer tissue-specific protease-cleavable linker (β) is fused to the heavy chain N-terminus of the Fv region that forms the immune cell antigen-binding region; and the number of amino acids in the fusion polypeptide is 16 or more to 65 or less when the cancer tissue-specific protease-cleavable linker (β) is fused to the light chain N terminus of the Fv region that forms the immune cell antigen-binding region. a multiple antigen-binding molecule (α) which comprises an immune cell antigen-binding region which recognizes an antigen that comprises a polypeptide consisting of the amino acid sequence QDGNE (SEQ ID NO: 15) and a cancer antigen-binding region which recognizes a cancer antigen; a cancer tissue-specific protease-cleavable linker (β) which comprises a polypeptide consisting of a target sequence of a cancer tissue-specific protease; and a masking molecule (γ) which comprises a polypeptide consisting of the amino acid sequence QDGNE (SEQ ID NO: 15); wherein the multiple antigen-binding molecule (α) and the masking molecule (γ) are linked via the cancer tissue-specific protease-cleavable linker (β), wherein the multiple antigen-binding molecule (α) is an antibody or an antibody fragment comprising at least two Fv regions, and the cancer antigen-binding region and the immune cell antigen-binding region are formed by different Fv regions, wherein the cancer tissue-specific protease-cleavable linker (β) is fused to a heavy chain N-terminus or a light chain N-terminus of the Fv region that forms the immune cell antigen-binding region, wherein the cancer tissue-specific protease-cleavable linker (β) and the masking molecule (γ) form a linear fusion polypeptide, and wherein the number of amino acids in the fusion polypeptide is eleven or more to 65 or less when the cancer tissue-specific protease-cleavable linker (β) is fused to the heavy chain N-terminus of the Fv region that forms the immune cell antigen-binding region; and the number of amino acids in the fusion polypeptide is 16 or more to 65 or less when the cancer tissue-specific protease-cleavable linker (β) is fused to the light chain N terminus of the Fv region that forms the immune cell antigen-binding region. <EOS>