To provide an illuminating system that has an illumination correcting function for an image processing apparatus, in particular, to provide an illuminating device and method for an image processing apparatus, which are able to change distribution of output from the illuminating device.

The illuminating device is used for the image processing apparatus that includes an imaging section for detecting image information of an inspection target and analyzes the image information of the imaging section. The illuminating device performs an illumination correction to the image information by using: an illuminating means for throwing light to the inspection target; a means for detecting illumination distribution of the image information detected by the imaging section; a comparison means for comparing the illumination distribution with a specific target distribution determined in advance; and a means for changing the luminance distribution of the illuminating means according to the result of output from the comparison means so that the illumination distribution has the target distribution.