A photographing unit photographs an object “n” times respectively with exposure times T1(1) to T1(n) to generate “n” sheets of images of the same object per an exposure time T1, where “n” is a whole number and the exposure times T1(1) to T1(n) are obtained by dividing the exposure time T1 by the whole number of “n”, a displacement correcting unit (32a, 32b) calculates a correction value for correcting displacement of the images, and a limb-darkening compensating unit (32d) corrects a position of a limb-darkening characteristic component of each of the images, using the correction value. Meanwhile, the limb-darkening characteristic components of the images whose positions have been corrected are combined to generate a limb-darkening characteristic component for compensation. Limb darkening in a combined image is compensated for, using the limb-darkening characteristic component for compensation, whereby a time required for performing a limb-darkening compensating process is decreased.