A method of encoding video information, comprising: determining an inter prediction mode of a current block (300; 910; 1000) as a merge mode, wherein the merge mode is an inter-prediction mode based on motion information of a merge candidate used as current motion information of the current block (300; 910; 1000); constructing merge candidates including a temporal merge candidate and spatial merge candidates (A0, A1, B0, B1, B2) of the current block (300; 910; 1000) based on a result of the determination; selecting a merge candidate of the merge candidates; deriving motion information of the selected merge candidate as motion information of the current block (300; 910; 1000), wherein the motion information includes a motion vector (600, 610, 620, 630) and a reference index; generating prediction samples for the current block (300; 910; 1000) based on the motion vector (600, 610, 620, 630) and a reference picture indicated by the reference index; generating residual samples based on the prediction samples; generating residual information for the current block (300; 910; 1000) based on the residual samples; and entropy encoding video information, wherein the video information includes the residual information for the current block (300; 910; 1000), merge mode information for whether the merge mode is applied to the current block (300; 910; 1000) and indication information indicating the selected merge candidate among the merge candidates, wherein the method is characterized in that a reference index of the temporal merge candidate is set equal to 0 regardless of any of values of reference indexes of spatial neighboring blocks, wherein the spatial merge candidates (A0, A1, B0, B1, B2) are derived using the spatial neighboring blocks of the current block (300; 910; 1000) and the temporal merge candidate is derived using a temporal collocated block, Col block, in a collocated picture, wherein the spatial neighboring blocks of the current block (300; 910; 1000) are a left bottom block A1, a right top block B1, a left-bottom corner block A0, a right-top corner block B0, and a left-top corner block B2 of the current block (300; 910; 1000), and wherein the temporal Col block is located at a position in the collocated picture corresponding to a position of the current block (300; 910; 1000). determining an inter prediction mode of a current block (300; 910; 1000) as a merge mode, wherein the merge mode is an inter-prediction mode based on motion information of a merge candidate used as current motion information of the current block (300; 910; 1000); constructing merge candidates including a temporal merge candidate and spatial merge candidates (A0, A1, B0, B1, B2) of the current block (300; 910; 1000) based on a result of the determination; selecting a merge candidate of the merge candidates; deriving motion information of the selected merge candidate as motion information of the current block (300; 910; 1000), wherein the motion information includes a motion vector (600, 610, 620, 630) and a reference index; generating prediction samples for the current block (300; 910; 1000) based on the motion vector (600, 610, 620, 630) and a reference picture indicated by the reference index; generating residual samples based on the prediction samples; generating residual information for the current block (300; 910; 1000) based on the residual samples; and entropy encoding video information, wherein the video information includes the residual information for the current block (300; 910; 1000), merge mode information for whether the merge mode is applied to the current block (300; 910; 1000) and indication information indicating the selected merge candidate among the merge candidates, wherein the method is characterized in that a reference index of the temporal merge candidate is set equal to 0 regardless of any of values of reference indexes of spatial neighboring blocks, wherein the spatial merge candidates (A0, A1, B0, B1, B2) are derived using the spatial neighboring blocks of the current block (300; 910; 1000) and the temporal merge candidate is derived using a temporal collocated block, Col block, in a collocated picture, wherein the spatial neighboring blocks of the current block (300; 910; 1000) are a left bottom block A1, a right top block B1, a left-bottom corner block A0, a right-top corner block B0, and a left-top corner block B2 of the current block (300; 910; 1000), and wherein the temporal Col block is located at a position in the collocated picture corresponding to a position of the current block (300; 910; 1000).