A foldable display device includes a display panel with a first display region, a second display region and a foldable display region located between the first and seconds display regions. A degradation information storage stores first degradation information for a first edge region and second degradation information for a second edge region. An edge information extractor extracts, in a first partial driving mode, first edge information for the first edge region from first partial image data, and extracts, in a second partial driving mode, second edge information for the second edge region from second partial image data. A gradation image generator generates, in the first partial driving mode, first gradation data based on the first edge information and the second degradation information, and generates, in the second partial driving mode, second gradation data based on the first degradation information and the second edge information.