1. An image processing method for performing image processing on an image to be processed, comprising: displaying a plurality of sample images generated by changing one or more image processing parameters used when the image processing is performed; setting, after the plurality of sample images are displayed on the display unit, one or more image processing parameters, which are used when the image processing is performed on the image to be processed, based on a mixing ratio among the plurality of sample images designated by an operator; and performing the image processing of the image to be processed based on the set image processing parameter.