To reduce the slackening of a yarn from a spinning device for spinning the yarn to a winder for winding the yarn in a spinning machine.

This slackening-reducing device is equipped with a slackening-reducing roller 23 for winding the yarn Y on its outer circumferential surface 23a, arranged so as to be engaged with the fibrous yarn spun by a spinning device of a spinning machine, a driving means 24 for rotatably driving the slackening-reducing roller 23 and a downstream side guide 26 for guiding the yarn Y on a rotation axis A of the slackening-reducing roller 23 for winding by supplying the yarn Y to a base end side B of the outer circumferential surface 23a of the slackening-reducing roller 23 and releasing the wound yarn Y from the tip end side D of the roller toward the downstream side guide 26, and also arranging an upstream side guide 25 by approaching the base end side B of the outer circumferential surface 23a of the slackening-reducing roller 23.