This invention discloses a force-saving damping device and a sliding door. The force-saving damping device is disposed between a first object and a second object. The second object slides relative to the first object in a first direction to close or slides in a second direction opposite to the first direction to open. It includes a blocking member, a damping member, a swinging member, and a linkage mechanism. The blocking member is pushed by the second object to slide in the same direction during the partial closing phase. The damping member buffers the second object when the blocking member slides in the first direction. The swinging member has a blocking surface and swings between a first state and a second state. In the first state, the blocking surface is adapted to be pushed in the second direction, and in the second state, the blocking surface is no longer pushed by the second object. When the swinging member slides in the second direction, it enters the second state from the first state, and vice versa. The linkage mechanism is placed between the blocking member and the swinging member, so that the blocking member and the swinging member are linked in the same direction and the
stroke of the swinging member is greater than the
stroke of the blocking member. This force-saving damping device makes opening the door easier.