During adjustment of a white balance, images having different white balances are displayed respectively on a plurality of regions on the screen 201 of the display 200, based on the red video signal Rout, the green video signal Gout and the blue video signal Bout output from the gamma correction device 30. After that, an user selects any of the plurality of regions by comparing the plurality of images having the different white balances displayed on the regions A to I on the screen 201 of the display 200 and pressing a touch panel on the screen 201. The image on the selected region is displayed on the entire screen 201 of the display 200, based on the red video signal Rout, the green video signal Gout and the blue video signal Bout output from the gamma correction device 30.