A display device is disclosed. The display device comprises: a storage configured to store output brightness information for each gradation according to brightness information of an image; and a processor configured to acquire target brightness corresponding to brightness information of an input image on the basis of the information stored in the storage, acquire a target light amount on the basis of a light amount of the input image, acquire a plurality of correction effects corresponding to a plurality of correction images by applying a plurality of gradation adjustment curves to the input image, acquire a gradation adjustment curve corresponding to the maximum correction effect among the plurality of correction effects, and adjust and output a gradation for each pixel of the input image on the basis of the acquired gradation adjustment curve.