Abstract: A foldaway treadmill is disclosed including: one pair of vertical posts interconnected by one cross bar, one base frame, one tread base, one supporting unit, one or a plurality of pneumatic-hydraulic cylinders, characterized in that, inside the said pneumatic-hydraulic cylinders, there are pneumatic-hydraulic chamber and compressing chamber, separated by piston whereon there is draining-functioned groove, filled with air and oil of suitable proportion to provide more safe, smooth and convenient folding up and out of foldaway treadmill than conventional ones.