1. An image processing device comprising: an image data acquisition unit that acquires, via an optical system, image data including a luminance component and a color difference component; a focusing distance acquisition unit that acquires a focusing distance of the optical system; a shading detection unit that detects shading of the luminance component included in the image data and detects shading of the color difference component included in the image data; a luminance shading correction coefficient calculation unit that, on the basis of the shading of the luminance component detected by the shading detection unit, calculates a luminance shading correction coefficient that is for correcting the shading of the luminance component, after the focusing distance is acquired by the focusing distance acquisition unit; a color difference shading correction coefficient calculation unit that, on the basis of the shading of the color difference component detected by the shading detection unit, calculates a color difference shading correction coefficient that is for correcting the shading of the color difference component, after the focusing distance is acquired by the focusing distance acquisition unit; a conversion unit that converts the color difference shading correction coefficient calculated by the color difference shading correction coefficient calculation unit so as to be at a predetermined ratio with respect to the luminance shading correction coefficient calculated by the luminance shading correction coefficient calculation unit; a first acquisition control unit that controls the image data acquisition unit so as to acquire a plurality of images by acquiring a plurality of sets of image data while altering an exposure condition, after the focusing distance is acquired by the focusing distance acquisition unit; a first correction unit that corrects the images acquired by the first acquisition control unit on the basis of the color difference shading correction coefficient converted by the conversion unit; a pixel addition unit that performs pixel addition of the images corrected by the first correction unit; a determination unit that determines whether a focusing distance which is acquired by the focusing distance acquisition unit after a correction by the first correction unit, has changed from the focusing distance acquired by the focusing distance acquisition unit before the correction by the first correction unit, after acquiring the plurality of sets of image data by the first acquisition control unit; a recording instruction detection unit that detects a recording instruction of an image; and a recording unit that, upon detecting a recording instruction of an image by the recording instruction detection unit after the correction by the first correction unit, records an image obtained by performing pixel addition by the pixel addition unit on the images corrected by the first correction unit, which are corrected based on a zoom position, when it is determined by the determination unit that the focusing distance acquired after the correction by the first correction unit has not changed from the focusing distance acquired before the correction by the first correction unit.