An exercise device capable of animating a walking motion is composed of a frame on which a damping unit, two drive units, and a handle are mounted. The drive units are respectively composed of a first frame, a second frame, a connection frame connecting the first frame and the second frame, a slide rod connecting the second frame and a crank of the damping unit, and a pedal rod fastened pivotally at one end thereof with the connection frame and at another end thereof with a roller capable of sliding on the slide rod. The drive units are driven at the same time in opposite directions when the pedal rods are at work, thereby resulting in the actuation of a rotary wheel for bringing about a leg exercise.