In gray-scale correction where extension to a dynamic range is performed based on a maximum value and a minimum value of a video luminance signal, sufficient correction effects cannot be obtained in some displayed images. Therefore, a histogram detecting circuit (2), a maximum value detecting circuit (3), and a minimum value detecting circuit (4) respectively detects, for each field, a maximum value (Kmax) and a minimum value (Kmin) in a detection WINDOW set in a screen, and distribution information in a gray-scale direction. The detected maximum value (Kmax) and minimum value (Kmin) are respectively corrected by a maximum value correcting circuit (5) and a minimum value correcting circuit (6) based on the output results of the histogram detecting circuit (2), and output as a corrected maximum value (Lmax) and a corrected minimum value (Lmin). Based on these corrected maximum value (Lmax) and a corrected minimum value (Lmin), an input video luminance signal is corrected. Thus, it is possible to obtain optimal effects of gray-scale correction in accordance with a scene.