To provide a material displacement preventive feeder for a flat stitch sewing machine suitably used for sewing material using a composite material such as a thin stretch material in particular by ensuring material feed in front and in the rear of a stitch forming position.

A flat stitch sewing machine having a throat plate 1 and a material presser foot 2 arranged to face in a vertical direction across the front and rear of the stitch forming position A, is provided with front upper and lower feed dogs 3, 4 arranged to face in the front upper and lower sides of the stitch forming position A, and a rear lower feed dog 5 arranged at the rear lower part of the stitch forming position A so as to face the front material presser foot 2. The rear upper part of the stitch forming position A is provided with rear upper feed dog 6 facing the rear lower feed dog 5, and the material B immediately after stitched is held and carried backward from the stitch forming position A by the rear upper feed dog 6 and the rear lower feed teeth 5.