A video decoding method in a multi-layer structure supporting scalability, comprising: constructing a merge candidate list for a current block in a current layer; deriving a motion vector for the current block based on the merge candidate list; deriving a prediction sample for the current block based on the motion vector for the current block; receiving residual information, which is a difference between the prediction sample and an original signal; reconstructing a current picture by adding the prediction sample and the residual; applying a deblocking filter to a block edge in the reconstructed current picture; and after the applying of the deblocking filter is complete, applying a band offset or an edge offset to a sample of the current picture, characterized in that when a value of inter-layer prediction enabled information is set equal to 0, the merge candidate list includes spatial candidates derived from spatial neighboring blocks in the current layer and a temporal candidate derived from a temporal neighboring block in the current layer, wherein the temporal candidate is positioned after the spatial candidates in the merge candidate list; when the value of the inter-layer prediction enabled information is set equal to 1, the merge candidate list includes spatial candidates derived from the spatial neighboring blocks in the current layer and an inter-layer candidate derived from a corresponding block in a reference layer which is different from the current layer, wherein the inter-layer candidate is positioned after the spatial candidates in the merge candidate list; when the value of the inter-layer prediction enabled information is set equal to 1, the inter-layer candidate is used, instead of the temporal candidate, for the merge candidate list; wherein a position of the inter-layer candidate in the merge candidate list for a case in which the value of the inter-layer prediction enabled information is set equal to 1 is the same as a position of the temporal candidate in the merge candidate list for a case in which the value of the inter-layer prediction enabled information is set equal to 0; wherein the inter-layer prediction enabled information is obtained through a slice segment header; and wherein a prediction mode of the current block is a merge mode, and a motion vector of a candidate indicated by a merge index in the merge candidate list is used as the motion vector for the current block. constructing a merge candidate list for a current block in a current layer; deriving a motion vector for the current block based on the merge candidate list; deriving a prediction sample for the current block based on the motion vector for the current block; receiving residual information, which is a difference between the prediction sample and an original signal; reconstructing a current picture by adding the prediction sample and the residual; applying a deblocking filter to a block edge in the reconstructed current picture; and after the applying of the deblocking filter is complete, applying a band offset or an edge offset to a sample of the current picture, characterized in that when a value of inter-layer prediction enabled information is set equal to 0, the merge candidate list includes spatial candidates derived from spatial neighboring blocks in the current layer and a temporal candidate derived from a temporal neighboring block in the current layer, wherein the temporal candidate is positioned after the spatial candidates in the merge candidate list; when the value of the inter-layer prediction enabled information is set equal to 1, the merge candidate list includes spatial candidates derived from the spatial neighboring blocks in the current layer and an inter-layer candidate derived from a corresponding block in a reference layer which is different from the current layer, wherein the inter-layer candidate is positioned after the spatial candidates in the merge candidate list; when the value of the inter-layer prediction enabled information is set equal to 1, the inter-layer candidate is used, instead of the temporal candidate, for the merge candidate list; wherein a position of the inter-layer candidate in the merge candidate list for a case in which the value of the inter-layer prediction enabled information is set equal to 1 is the same as a position of the temporal candidate in the merge candidate list for a case in which the value of the inter-layer prediction enabled information is set equal to 0; wherein the inter-layer prediction enabled information is obtained through a slice segment header; and wherein a prediction mode of the current block is a merge mode, and a motion vector of a candidate indicated by a merge index in the merge candidate list is used as the motion vector for the current block.