An image decoding method according to the present invention comprises the steps of: deriving at least one merge candidate on the basis of at least one of a spatial neighboring block and a temporal neighboring block of a current block; generating a merge candidate list including the merge candidate; acquiring LX direction motion information of the current block, from a first merge candidate included in the merge candidate list; acquiring L(1-X) direction motion information of the current block, from a second merge candidate different from the first merge candidate; and performing inter-prediction on the basis of the LX direction motion information and the L(1-X) direction motion information.