An image processing apparatus is provided with an optical system to for irradiating light to an image document, for detecting light transmitting through the image document or light reflected from the image document and for converting the light into electric signals, thereby obtaining a first image information, the optical system having an amount of flare; a flare amount memory for memorizing an amount of flare of the optical system; a flare component calculator for obtaining a flare component contained in the first image information on the basis of the first image information and the flare amount of the optical system; and a controller for determining on the basis of the flare component a copy condition on which the image document is copied.