An image processing method of obtaining a image proper for diagnosis from a radiation image having signals corresponding to an irradiation dose of radiation having passed through a radiographed object, comprising: an image processing step of conducting an image processing on an image processing condition including at least one or more parameters having a preliminarily-set default value; an image processing condition adjusting step of adjusting the image processing condition; an adjustment result recording step of recording the adjustment result of the parameters in the image processing condition adjusted in the image processing condition adjusting step; a parameter changing step of renewing the default value of at least one of the parameters in the image processing condition based on adjustment results of plural time adjustments recorded in the adjustment result recording step.