To apply necessary and sufficient sharpness emphasizing process to a busy subject in which noise component is not conspicuous, and apply weak sharpness emphasizing process to a subject which is not busy and in which noise component is conspicuous, when sharpness emphasizing process is performed to an original image.

Local standard deviation expressing the change of original image data in a prescribed region is calculated from the original image data (step 100). A normalized index value expressing the degree of business of an image is formed from the standard deviation (step 102). A sharpness emphasis coefficient for setting intensity of sharpness emphasis wherein a value changes monotonously in accordance with the increase of the formed index value (step 104). By using the sharpness emphasis coefficient, the sharpness emphasizing process is applied to the original image data (step 106).