An electric treadmill with a folding mechanism by use of two swivel pieces includes a handrail frame mounted at both sides of the front end of the base frame. A base frame swivel piece is pivotally positioned at both sides near the front part of the bottom of the base frame, respectively. A handrail frame swivel piece is pivotally disposed near the bottom of the handrail frames, respectively. A pull rod is pivotally interposed between the swivel pieces. A movable support with ground-touching rollers is pivotally coupled to a cross shaft of the base frame swivel pieces. Moreover, the movable support is constantly biased by a telescopic supporting element. In this way, an action bar of the telescopic supporting element pushes the movable support forward when the base frame is folded upwards. Meanwhile, the ground-touching rollers are constantly in contact with the ground. Accordingly, a stable folded-up position is achieved.