A method of decoding motion information may include: obtaining, from a bitstream, change information indicating whether to change motion information of a neighboring block; when the change information indicates a change of the motion information and a higher block is able to use one reference picture list, identifying the number of pictures included in the reference picture list of the current block; selecting, as a reference picture of the current block, a reference picture of the neighboring block based on the number of pictures; when the reference picture of the neighboring block is selected as the reference picture of the current block, obtaining a motion vector of the current block by applying an offset to a motion vector of the neighboring block; and reconstructing the current block by using a reference block indicated by the motion vector of the current block in the reference picture of the current block.