1. An image processing method for removing noise contained in an image, comprising: inputting an original image constituted with a plurality of pixels; extracting a first high-frequency component through first high-pass filter processing executed on the original image; extracting a second high-frequency component through second high-pass filter processing executed on the extracted first high-frequency component; extracting a noise component by separating the noise component through nonlinear conversion processing executed on the extracted second high-frequency component; and removing the noise in the original image based upon the extracted noise component.