To provide a yarn winding machine capable of reliably detecting a small amount of yarn portion remaining on a yarn storage roller after cutting the yarn.

A spinning machine 1 includes a winding device 12, a yarn clearer 11 for detecting any defect of a yarn 16 to be wound around the winding device 12, a cutter 10 for cutting the yarn 16 when detecting any yarn defect by the yarn clearer 11, and a slack eliminating device 8 arranged between the winding device 12 and the cutter 10. The slack eliminating device 8 includes a slack eliminating roller 30 and a yarn detecting sensor 34 consisting of a reflective photo sensor having a light emitting element 41 and a light receiving element 42. An opening formed in the light emitting element 41 has the prescribed width such that a width of an irradiated range on the slack eliminating roller 30 is substantially equal to the thickness of the yarn 16.