1. An image pickup apparatus having image pickup means for imaging a subject, comprising: weighting means for weighting luminance information of pixels in a predetermined area with respect to luminance information of the subject image taken by the image pickup means; exposure control means for conducting an exposure at the time of imaging the subject by the image pickup means on the basis of the luminance information obtained by weighting the luminance information of pixels in the predetermined area by the weighting means; relevant information acquisition means for acquiring relevant information indicative of a difference in brightness between the predetermined area and the other area than the predetermined area of a reference image, which has been taken by an image pickup operation involving the exposure control of the exposure control means immediately before the subject is regularly imaged by the image pickup means, on the basis of luminance information of the reference image; storage means for storing proper exposure information indicative of proper exposure corresponding to the brightness of the subject; photometry means for measuring the brightness of the subject when the reference image is taken by the image pickup means; compensating means for compensating the proper exposure information stored in the storage means in response to the brightness of the subject measured by the photometry means, in accordance with the difference in brightness indicated by the relevant information acquired by the relevant information acquisition means; and control means for causing the exposure control means to perform exposure control for proper exposure indicated by the proper exposure information after compensated by the compensating means when the subject is regularly imaged by the image pickup means.