An image processing apparatus allows appropriate image processing with high versatility regardless of a site of a test subject and setting by an operator.There are provided a gradation transformation processing section 162 that performs gradation transformation processing on image data obtained by photographing a subject, based on a gradation transformation characteristic having a predetermined shift amount S and gradient G, a frequency enhancement processing section 163 that performs frequency enhancement processing on the image data having been subjected to the gradation transformation processing, based on a frequency enhancement characteristic being a characteristic of enhancement degrees for respective frequencies, and an image processing condition calculation section 130 that determines the gradation transformation characteristic and calculates the frequency enhancement characteristic, based on the gradation transformation characteristic. Herein, the image processing condition calculation section calculates a gradation transformation characteristic having a small gradient G so that frequency enhancement processing can be performed from a low frequency region, and calculates a frequency enhancement characteristic, based on the gradation transformation characteristic.
