Looper section (5) provided under a needle plate (8) includes: a plurality of loopers (18) arranged in an array along a curved movement path; and a movement mechanism (13, 17, 19, 28) for moving the plurality of loopers (18) along the curved movement path to selectively position one of the plurality of loopers in a predetermined needle drop position. Chain-stitch sewing is performed by cooperation between the one looper (18) selectively positioned in the needle drop position and a hooked needle (4). The looper section (5) projects at its one end portion including the predetermined needle drop position, and a cylindrical sewing workpiece can be taken to and from the needle drop position via the one projecting end portion. The curved movement path is, for example, a U-shaped path.