The control unit 10 determines whether the resolution of the original digital image (original) is equal to or higher than first predetermined times the resolution of the target resolution (for example, twice, √2 times, or 1.5 times), based on the resolution of the original digital image (original) and the target resolution decided at Step S1 (Step S3). Upon determination that the resolution is equal to or higher than first predetermined times the resolution of the target resolution (S3: YES), the control unit 10 determines whether the resolution of the original digital image (original) is equal to or lower than second predetermined times the resolution of the target resolution (higher than first predetermined times) (Step S4). At Step S4, upon determination that the resolution of the original digital image is equal to or lower than second predetermined times the resolution of the target resolution (S4: YES), the control unit 10 temporarily stores the original digital image (original) with the original resolution in a built-in memory or the storage unit 12 as a temporary reference image.

At Step S3, upon determination that the resolution is lower than first predetermined times the resolution of the target resolution (S3: NO), the control unit 10 generates a super-resolution image with a resolution first predetermined times the resolution of the target resolution with respect to the original digital image (original), according to processing by the image processing unit 11 based on the super-resolution model 1M (Step S6). The control unit 10 temporarily stores the generated super-resolution image as the temporary reference image in a built-in memory or the storage unit 12 (Step S7).