A waistband sew-in device to carry out. The sewing of waistbands in the waist part of briefs, skirts and trousers by retaining a cloth in a hoop shape with a stationary frame equipped with an inverted two-legged U-shaped guide surface, inserting a stretched waistband outside the cloth, folding over a cloth edge of the cloth in two plies to the outside of the waistband, further folding the cloth edge of the already folded part in two plies to be pushed into the space between the waistband and the cloth, sliding a belt strip reeled on the guide surface of the stationary frame on the guide surface by a take-up and rewinding mechanism installed on each leg of the two legs of the stationary frame, and sending the cloth having the waistband reeled in its three-folded cloth edge into a sewing unit of a sewing machine together with said waistband.