The invention naturally enhances the sharpness of an image by performing appropriate sharpness processing. An image processing device receives input original image data, performs sharpness processing, and outputs correction image data. Specifically, the degree of the level change is detected from the original image data, and correction-reference-amount data, which provides a reference to determine the degree of sharpness correction, is determined based on the degree of the detected level change. Meanwhile, the relationship between correction amount by which the sharpness correction is performed and the correction reference amount is defined by a predetermined correction-amount characteristic pattern. The correction-amount calculating device calculates an adequate correction amount in accordance with the correction-amount characteristic pattern, and the sharpness processing means performs sharpness processing on the original image data in accordance with the correction amount. In this case, the correction determining pattern has a characteristic that the correction amount varies in accordance with the magnitude of the correction reference amount. Thus, in accordance with a level change in the original image data, the sharpness correction is performed by an adequate correction amount, which can sharpen the original image data to an adequate degree.