Method and device for encoding/decoding image

The invention relates to a method and an apparatus for encoding/decoding an image. The method of decoding an image includes: determining whether a merge mode is applied to a current block; when the merge mode is applied to the current block, determining whether geometric modification information is used for inter prediction of the current block based on geometric modification usage information of the current block; when the geometric modification use information indicates that the geometric modification information is used for inter prediction of the current block, obtaining a prediction block of the current block within the decoding target picture by performing inter prediction based on the reference picture and the geometric modification information; and obtaining a reconstructed block of the current block by summing the prediction block and the residual block, in which geometric modifications for geometric modification information include affine modifications, and in which the geometric modification inform