The invention discloses a sewing device. The sewing device comprises a rack, a sewing machine supported on the rack and a tension mechanism positioned at the feeding side of the sewing machine and used for making a stitching edge of a material to be stitched have certain pre-tension force; the tension mechanism comprises a guide rail supported on the rack in a feeding direction and a clamping mechanism arranged on the guiding rail in a sliding mode and used for clamping one end of the stitching edge tightly. The sewing device can ensure the pre-tension force performed on the stitching edges during stitching, make the stitching edges always maintain flush and reduce the stitching cost.