An image processing method of obtaining a suitable image for diagnosis from a radiation image having signals according to an irradiation amount of a radiation ray transmitting through a subject, the image processing method includes: a feature amount calculating step of calculating a feature amount a feature amount evaluating step of evaluating the feature amount calculated with a feature amount evaluating function in the feature amount calculating step a parameter determining step of determining a parameter for an image processing on a result evaluated in the feature amount evaluating step and an image processing step of processing an image using the parameter determined in the parameter determining step.