A thin safety door includes a baffle, a supporting frame and an elastic element. The baffle is provided with a front slope and a rear slope. The baffle is provided with a pair of sliders disposed side by side at a position between the front slope and rear slope of the baffle. A pair of slide ways are disposed on the left side and right side of the supporting frame. The baffle spans the supporting frame and the sliders are connected to the slide ways, so that the baffle can slide relative to the supporting frame. The elastic element abuts against the baffle, so that an elastic force is applied to the sliders of the baffle for returning to a higher position when located on the slide ways.