To provide a sewing machine belt loop feed device capable of slackening a belt.

A delivery part travels along a route between a belt feed means and a means 6 for bending a belt 12 like a loop. In this case, the delivery part is divided into a plurality of parts, and the belt 12 is slackened by changing the travel distance of both ends thereof. Alternatively, the belt 12 is slackened by providing a slackening rod in the vicinity of the center of the belt 12, when the delivery part so divided travels.