The invention provides a preparation method and a preparation device for a CIGS-based thin-film solar cell. According to the invention, a light absorption layer of the CIGS-based thin-film solar cell is deposited by adopting double-target sputtering in a vacuum chamber, a plasma ablation area of a target 1 faces towards the direction of a substrate and a plasma ablation area of a target 2 faces towards the surface of the target 1 in the sputtering process, so that materials of the target 2 are deposited on the target 1, and then the materials of the targets 2 are deposited on the substrate together with materials of the target 1. The preparation method for the light absorption layer enables components of the deposited film to be more uniform.