1. An image processing method for carrying out a predetermined image quality correction for correcting a predetermined image quality on each of a plurality of images in an image group to obtain respective corrected images, comprising the steps of: using one or more processors to perform steps of: carrying out a predetermined temporary image quality correction for correcting the predetermined image quality on each of the plurality of images in the image group to obtain a temporarily corrected image of each of the plurality of images, calculating a characteristic value representing the predetermined image quality for each temporarily corrected image, calculating a target characteristic value so that dispersion of each characteristic value to the target characteristic value is minimized on the basis of the characteristic value of each temporarily corrected image, obtaining a correction value of each of the plurality of images in the image group which corrects the characteristic value thereof to the target characteristic value, and correcting the image with the correction value, wherein in the step of calculating the characteristic value, the characteristic value is calculated for each of a plurality of partial areas constituting the temporarily corrected image; wherein in the step of calculating the target characteristic value, the target characteristic value is calculated for each of the plurality of partial areas by using the characteristic value for each of the plurality of partial areas, respectively; and wherein in the step of obtaining the correction value, the correction value of each of the plurality of images in the image group is obtained so that the characteristic value of each of the partial areas becomes the target characteristic value of each of the partial areas, respectively.