The backlight apparatus allows brightness control with minimum
image quality deterioration. This apparatus has: an illuminating section (20) that radiates illumination light on a back of a
liquid crystal panel (10) which comprises a plurality of
image display areas and which displays an image by modulating per
image display area the illumination light according to an
image signal; and a brightness determining section (30) that determines a
light emission brightness value of the illuminating section (20) and renews a light emitting state of the illuminating section (20), based on the determined
light emission brightness value, and the illuminating section (20) has a plurality of light emitting areas illuminating each of a plurality of
image display areas, and the brightness determining section (30) determines a
light emission brightness value of the first image display area, from values acquired by applying weights to the first information based on an input
image signal of the first image display area and the second information based on the input
image signal of the second image display areas, and changes the weights for the first information and the second information based on luminance of ambient light surrounding the backlight apparatus.