1. A video encoding method for reducing encoding error by using a loop filter, the method comprising: generating a reconstructed image from encoded data of an original image; determining one or more regions on which the loop filter is applied in the reconstructed image; 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.