An overedge sewing machine adapted to perform three thread overedge stitching (Stitch Types 504 and 505) under the cooperating action of one needle (6) and an upper looper (15) and a lower looper (31). In addition to swing movement in the direction crossing the fabric feed direction, reciprocating movement in the fabric feed direction is selectively applied to the lower looper, whereby the front end of the lower looper is revolved around the needle. If the lower looper is revolved around the needle with the upper looper out of action, this operation provides double chain stitching (Stitch Type 401). Further, if the lower looper is revolved around the needle with the upper looper in action, this operation provides three thread double chain overedge stitching (Stitch Type 601).