1. An image processing method adopted to remove noise present in an image, comprising: an image input step in which an original image constituted of a plurality of pixels is input; a multiple resolution image generation step in which a plurality of low-frequency images with resolutions decreasing in sequence and a plurality of high-frequency images with the resolutions decreasing in sequence are generated by decomposing the input original image; a noise removal processing step in which noise removal processing is individually executed on the low-frequency images and the high-frequency images; and an image acquisition step in which a noise-free image of the original image is obtained based upon both the low-frequency images and the high-frequency images having undergone the noise removal processing, wherein in the image acquisition step, noise removal processing is executed in a real space assuming a resolution matching a resolution of the original image and image data of the noise-free image of the original image are obtained by handling results of noise removal executed in the real space together with results of noise removal from the low-frequency image.