A liftable and foldable treadmill includes a base frame provided with two sliding tracks, a running platform provided at the top side of the base frame, two sliding devices arranged at the front side of the running platform, a lift frame having a front coupling portion pivotally connected to the running platform, a folding frame having a rear coupling portion pivotally connected to the base frame, and a linear brake arranged at the running platform. When folding the running platform, the two sliding tracks are respectively inserted into an upward opening in each of the sliding tracks and moved backwards along the sliding tracks. The linear brake includes an output bar extending downwards and pivotally connected to the lift frame for enabling the front side of the running platform to be lifted. Thus, the lifting and folding mechanisms of the treadmill commonly have a simple structure.