A medical gymnastic treadmill is disclosed to include two handrail assemblies each having a horizontal top rail a plurality of screw rods pivotally supported on the base frame of the treadmill body, vertical tubes respectively coupled between the top rail and the screw rods, a reversible motor, and a transmission mechanism coupled between the reversible motor and the screw rods for rotating the screw rods to move the tubes and top rails of the two handrail assemblies to the desired elevation at the same time upon rotation of the reversible motor.