An image decoding method performed by a decoding apparatus, according to the present invention, comprises the steps of: acquiring information on a first SAO and information on a second SAO of a current block through a bit stream; generating a reconstructed block of the current block; and performing an SAO procedure for the reconstructed block on the basis of the first SAO and the second SAO, wherein the information on the first SAO comprises first offset type information applied to the first SAO and first offset value information for n offset values, and the information on the second SAO comprises second offset type information applied to the second SAO and second offset value information for m offset values. According to the present invention, an efficient SAO procedure can be performed on the basis of a plurality of SAOs, and the video quality of images can be further improved.