A video decoding method, the method comprising: obtaining video information including picture reconstruction information and offset information from a bitstream; reconstructing a picture on the basis of the picture reconstruction information; and applying an in-loop filter to the reconstructed picture, wherein the step of applying the in-loop filter includes the steps of: applying a deblocking filtering process to the reconstructed picture; and applying a sample adaptive offset process to the reconstructed picture on the basis of the offset information after completing process of the deblocking filtering, wherein the offset information includes first offset information indicating whether the sample adaptive offset process is enabled and second offset information for applying an offset to a sample when the first offset information indicates that the sample adaptive offset process is enabled, wherein the second offset information includes offset type information for specifying an offset type for the sample, wherein the offset type information indicates that a band offset is applied to the sample, wherein the second offset information includes information on offset values for multiple bands, characterized in that the second offset information includes start band information explicitly indicating a variable start of the multiple bands to determine together with end band information indicating a variable end of the multiple bands a band group comprising the multiple bands among 32 bands, the band information being different from the offset type information, wherein an offset value, corresponding to a band among the multiple bands is applied to the sample. obtaining video information including picture reconstruction information and offset information from a bitstream; reconstructing a picture on the basis of the picture reconstruction information; and applying an in-loop filter to the reconstructed picture, wherein the step of applying the in-loop filter includes the steps of: applying a deblocking filtering process to the reconstructed picture; and applying a sample adaptive offset process to the reconstructed picture on the basis of the offset information after completing process of the deblocking filtering, wherein the offset information includes first offset information indicating whether the sample adaptive offset process is enabled and second offset information for applying an offset to a sample when the first offset information indicates that the sample adaptive offset process is enabled, wherein the second offset information includes offset type information for specifying an offset type for the sample, wherein the offset type information indicates that a band offset is applied to the sample, wherein the second offset information includes information on offset values for multiple bands, characterized in that the second offset information includes start band information explicitly indicating a variable start of the multiple bands to determine together with end band information indicating a variable end of the multiple bands a band group comprising the multiple bands among 32 bands, the band information being different from the offset type information, wherein an offset value, corresponding to a band among the multiple bands is applied to the sample. applying a deblocking filtering process to the reconstructed picture; and applying a sample adaptive offset process to the reconstructed picture on the basis of the offset information after completing process of the deblocking filtering, wherein the offset information includes first offset information indicating whether the sample adaptive offset process is enabled and second offset information for applying an offset to a sample when the first offset information indicates that the sample adaptive offset process is enabled, wherein the second offset information includes offset type information for specifying an offset type for the sample, wherein the offset type information indicates that a band offset is applied to the sample, wherein the second offset information includes information on offset values for multiple bands, characterized in that the second offset information includes start band information explicitly indicating a variable start of the multiple bands to determine together with end band information indicating a variable end of the multiple bands a band group comprising the multiple bands among 32 bands, the band information being different from the offset type information, wherein an offset value, corresponding to a band among the multiple bands is applied to the sample.