To provide a yarn cooling apparatus capable of changing blowout length corresponding to brand, especially brand having a thick fineness, in a cylindrical yarn-cooling apparatus.

The yarn cooling device 3 is installed under a spinneret 1 having a spinning hole group bored multiple concentrically in order to extrude a melted thermoplastic polymer and spin the polymer as a multifilament and a yarn, and further, a cylindrical cooling air-blowing surface for radially blowing out cooling air for cooling a spun yarn 2 traveling the interior from the outer peripheral side to the inner peripheral side of yarn. In the yarn cooling device, a cooling length-regulating member 11 capable of freely regulating the length of the blowing out cooling air from cooling air-blowing out face is fitted and inserted from the lower end along the inner wall face and/or the outer wall face of the cylindrical cooling air blowing surface so that cooling length of the cooling air-blowing surface is adjustable.