A snow ski traction device includes a traction blade pivotally mounted on blade-to-ski attachment device so as to secure the blade to the side of a snow ski. The blade pivots through a pivot arc of substantially 90 degrees and is stopped from pivoting outside of that arc. At one end of the arc, the length of the blade is substantially parallel to the length of the ski; while at the other end of the arc, it is perpendicular to the length of the ski. When perpendicular to the ski, the blade engages with and presses backwards against snow or ice beneath the ski, thus propelling the wearer of the ski in a forward direction and preventing backward slippage of the ski. When parallel to the ski, the blade permits a full, forward sliding movement of the ski. The ordinary motion of the ski causes the blade to pivot as required between these parallel and perpendicular positions. This device, and its method of use, are particularly applicable for cross-country skiing, though can be used by downhill skiers as well.