An image evaluation device, comprising: a difference determination unit (25, 335) configured to determine, for each region corresponding to a coding unit of an object image, a presence or absence of a difference between a small image of the region and small images of adjacent regions based on an amount of coding bits in a coding process of the region of the object image and the amount of coding bits of the adjacent regions, and determine, if the presence of the difference is determined, a presence or absence of a further difference between the small image of the object image and the small image, spatially having the same position as the small image of the object image, of a region corresponding to the coding unit of each of reference images, respectively, based on the amount of coding bits of the small image of the object image and the amount of coding bits of the small image of each of the reference images, the object image being one of a plurality of encoded images that include three or more time-series encoded images obtained by imaging the same spatial region, and the reference images being images other than the object image among the plurality of images, and determine a presence or absence of a difference between the object image and the each of the reference images, based on the determination result of determining the presence or absence of the difference between the each small image of the object image and the each small image of the each of reference images; and an evaluation index acquisition unit (26, 336) configured to acquire an evaluation index for the object image on the basis of at least one of the number of determinations of the presence of the difference between the object image and the each of the reference images and the number of determinations of the absence of the difference between the object image and the each of the reference images, wherein the evaluation index acquisition unit (26, 336) is configured to acquire a ratio of a number of the reference images determined to have the difference from the object image to a total number of reference images among the plurality of images as the evaluation index for the object image, and determine that the object image do not satisfy a quality standard when the ratio is greater than or equal to a threshold value. a difference determination unit (25, 335) configured to determine, for each region corresponding to a coding unit of an object image, a presence or absence of a difference between a small image of the region and small images of adjacent regions based on an amount of coding bits in a coding process of the region of the object image and the amount of coding bits of the adjacent regions, and determine, if the presence of the difference is determined, a presence or absence of a further difference between the small image of the object image and the small image, spatially having the same position as the small image of the object image, of a region corresponding to the coding unit of each of reference images, respectively, based on the amount of coding bits of the small image of the object image and the amount of coding bits of the small image of each of the reference images, the object image being one of a plurality of encoded images that include three or more time-series encoded images obtained by imaging the same spatial region, and the reference images being images other than the object image among the plurality of images, and determine a presence or absence of a difference between the object image and the each of the reference images, based on the determination result of determining the presence or absence of the difference between the each small image of the object image and the each small image of the each of reference images; and an evaluation index acquisition unit (26, 336) configured to acquire an evaluation index for the object image on the basis of at least one of the number of determinations of the presence of the difference between the object image and the each of the reference images and the number of determinations of the absence of the difference between the object image and the each of the reference images, wherein the evaluation index acquisition unit (26, 336) is configured to acquire a ratio of a number of the reference images determined to have the difference from the object image to a total number of reference images among the plurality of images as the evaluation index for the object image, and determine that the object image do not satisfy a quality standard when the ratio is greater than or equal to a threshold value.