An image-processing method of removing noise from an image includes: obtaining standard representative values for standard regions of a standard image and reference representative values for reference regions of a reference image, and obtaining a plurality of hierarchical images having different resolutions with respect to the standard image and the reference image based on the standard representative values and the reference representative values; obtaining the standard representative values for the standard regions of the standard image and the reference representative values for the reference regions of the reference image from the hierarchical images; determining a similarity between the standard regions and the reference regions from the standard representative values and the reference representative values; and removing noise by applying filtering to the standard image and the reference image depending on the determined similarity.