1. A video encoding method using a loop filter, the method comprising: generating a reconstructed image from encoded data of an original image; determining, in the reconstructed image, one or more regions on which the loop filter is applied; transforming the original image and the reconstructed image which correspond to each region of the determined one or more regions from a spatial domain into a frequency domain; determining loop filter coefficients for said each region by comparing the transformed original image and the transformed reconstructed image; loop-filtering the reconstructed image based on the loop filter coefficients for said each region; and encoding information on the loop filter coefficients for said each region, wherein the loop-filtering of the reconstructed image comprises: loop-filtering the transformed reconstructed image in the frequency domain, by using the loop filter coefficients for said each region; and inversely transforming the transformed reconstructed image loop-filtered in the frequency domain.