A treadmill includes a base and a frame having a first end pivotably connected to the base by two parallel first links and two parallel second links. An endless belt is mounted to the frame. Two respective first ends of the two first links are pivotably connected to two respective first pivotal points on the two side rails of the base, and two respective second ends of the two first links are pivotably connected to two respective second pivotal points on two sides of the first end of the frame. Two respective first ends of the two second links are pivotably connected to two respective third pivotal points on the two side rails of the base, and two respective second ends of the two second links are pivotably connected to two respective fourth pivotal points on the two sides of the first end of the frame. The frame can be pivoted relative to the base by the first and second links.