A bonding device includes: a stage and a pressing part, which is placed on the stage and is movable toward the stage. A first layer, which is disposed on an upper surface of the stage, includes a first flat portion and first bending portions. A second layer, which is disposed below a lower surface of the pressing part, includes a second flat portion and second bending portions. The first and second bending portions may be disposed between the stage and the pressing part, in a state bent with curvatures, respectively. The curvature of a lower surface of each of the second bending portions is smaller than the curvature of an upper surface of each of the first bending portions.