A difference sample data holder of a gamma correction device holds as difference sample data a difference between a corrected signal level and a yet-to-be-corrected signal level for each of multiple sample points set at equal intervals between the permissible minimum and maximum levels of an input video signal. A correction execution unit performs cubic interpolation operation using the difference sample data held in the difference sample data holder, and adds the operated result and the signal level of the input video signal to obtain the signal level of the corrected video signal.