Inter prediction mode-based image processing method and apparatus therefor

An apparatus for processing an image based on an inter prediction mode, the apparatus comprising:

• a candidate group construction unit configured to check merge candidates according to a predetermined sequence and configuring a plurality of candidate groups;
• a group index extraction unit configured to extract a group index indicating a specific candidate group among the plurality of candidate groups;
• a merge index extraction unit configured to extract a merge index indicating a specific merge candidate within a candidate group indicated by the group index;
• and
• a prediction block generation unit configured to generate a prediction block of a current block using motion information of a merge candidate indicated by the merge index,
• wherein the plurality of candidate groups includes a first candidate group including motion information of a spatial neighbor block of the current block and a second candidate group including motion information of a temporal neighbor block of the current block.