A conjugation device includes at least one flow reactor having an inlet and an outlet, the flow reactor(s) being completely filled with a support such as a matrix including 1) chromatography beads, fibers or membranes, and 2) a biologic catalyzer, namely the enzyme ligase, which is immobilized onto this support; a fluid delivery unit in fluid communication with the inlet of the flow reactor(s) and configured to continuously provide the flow reactor(s) with at least one kind of reaction fluid such as antibody and linker-payload according to stages of the conjugation process, the at least one kind of process fluid including a first moiety and a second moiety of a conjugate to be produced; and a fluid collection unit in fluid communication with the outlet of the flow reactor(s) and configured to control collection of fluid flowing out of the outlet of the flow reactor(s) according to the stages of the conjugation process. In a period of enabling the at least one kind of reaction fluid to continuously flow through the flow reactor(s), a conjugation reaction is conducted between the first moiety and the second moiety under catalysis of the ligase to produce the conjugate.