An antibody-drug conjugate having a cyclic benzylidene acetal linker represented by formula (1) or formula (2), wherein Y is an antibody； D is a drug； R1 and R6 are each independently a hydrogen atom or a hydrocarbon group； R2, R3, R4 and R5 are each independently an electron-withdrawing or electron-donating substituent or a hydrogen atom； s is 1 or 2, t is 0 or 1, and s+t is 1 or 2； w is an integer of 1 to 20； and Z1 and Z2 are each independently a selected divalent spacer:
