1. An image processing device which uses a representative picture having a first resolution and a plurality of reference pictures having the first resolution that are related to the representative picture to generate a target high-resolution picture having a second resolution higher than the first resolution, said image processing device comprising: a first repetition processing unit operable to repeat positioning processing while switching from one reference picture to another; and a second repetition processing unit operable to repeat update processing for updating a value of a pixel in the target high-resolution picture after completion of the positioning processing performed by said first repetition processing unit; wherein, in the positioning processing, an amount of displacement of a reference picture from the representative picture is estimated and, on the basis of an estimated amount of the displacement, a pixel of the reference picture is located at a sub-pixel position in a high-resolution picture produced by enlarging the representative picture, and in the update processing, the value of the pixel in the target high-resolution picture is updated so that a value of an evaluation function is decreased, the evaluation function including, as a variable, the difference between a value of a pixel in the positioned low-resolution pixel and the value of the pixel in the target high-resolution picture, and at least one of said first and second repetition processing units includes: a determination unit operable to determine a pixel that satisfies a completion condition from a result of one of the positioning processing and the update processing; and an exclusion unit operable to exclude the pixel that satisfies the completion condition from one of the positioning processing and the update processing.