To provide a brightness adjustment device which makes the gamma correction of a display device while correcting the dynamic range of an input video image signal with simple circuit configurations.

On the assumption that the dynamic range of an input signal is a full range, the gamma correction data 105 necessary for the correction circuit for broken gamma rays, is found, by inverting the gamma characteristics 102 of a displaying device in order to make the desired output brightness curve 104 compliant with an adjustment value group 103 as a user desires under the condition. Then, a dynamic range correction calculation 106 is made, which is to be resampled by the input signal after the dynamic range correction, and the dynamic range correction data 107 is set to a broken gamma rays correction circuit 101 as the input signal before the dynamic range correction, to adjust the dynamic range of the input video image signal.