A thread cutter for a chain stitch sewing machine which performs chain stitch sewing by cooperation of a needle driven up and down and a looper arranged under a needle plate, including: a movable knife arranged so that it can advance into or retract from a gap between a top surface of the looper and an under surface of the needle plate; a knife driving mechanism for advancing and retracting the movable knife; a stationary knife arranged under the needle plate for cutting a sewing thread in cooperation with the movable knife when the movable knife is retracted; and a thread holding plate for holding a cut end of the sewing thread on the side of the looper in a predetermined position by a further retracting operation of the movable knife after the sewing thread is cut and a drive unit for a multi-sewing machine.