A mechanical stretching device for automatically folding a movable sofa leg includes a mechanical stretching device, a switching device, and an automatic folding device. The switching device includes a handle ring (1), a handle shank (3), a handle support (6) and a handle spring (5). The automatic folding device includes an automatic rotating part (8), a rotating tube (21), a spring hanging piece (17), folding spring (10). The handle ring (1) is rotatably connected to the handle shank (3). Handle shank (3) is rotatably connected to the handle support (6). The handle support (6) is fixed on the base frame mounting plate (20). The rotating tube (21) is rotatably connected to the base frame mounting plate (20). The automatic rotating part (8) is fixed on the rotating tube (21). The spring hanging piece (17) is rotatably connected to the automatic rotating part (8).
