The embodiments of the present application provide an attachment device and an attachment method, being used for attaching a curved cover plate to a flexible screen. The attachment device comprises: a flexible bearing plate used for supporting a flexible screen, the flexible bearing plate comprising a top wall and two side walls, the top wall having a central backbone portion and bearing portions, the top wall being connected to the side walls by means of the bearing portions, and the side walls and the top wall enclosing a hollow space; and an elastic support assembly located in the hollow space, the elastic support assembly being configured to be deformable, such that the flexible bearing plate can deform from a first state to a second state under the pressing effect of the curved cover plate, wherein in the first state, the flexible bearing plate has a ridge shape, and the bearing portions are connected between the central backbone portion and the side walls in an inclined manner, such that during the process of moving the flexible bearing plate from the first state to the second state, the degree of inclination of the bearing portions gradually decreases. According to the embodiments of the present application, air bubbles between the curved cover plate and the flexible screen can be effectively removed, increasing the product yield.