1. A method of decoding an image, the method comprising: obtaining, by a decoder comprising a processor, a prediction mode of a current block, from a bitstream; when the prediction mode of the current block is inter-prediction, obtaining a spatial motion vector predictor candidate of the current block by using a motion vector of an available spatial block spatially related to the current block; obtaining a temporal motion vector predictor candidate of the current block by using a motion vector of an available temporal block temporally related to the current block; adding, when a number of the spatial motion vector predictor candidate and the temporal motion vector predictor candidate is smaller than a predetermined number n, where n is an integer equal to two or greater, a zero vector to be a motion vector predictor candidate so that a number of motion vector predictor candidates is to be the predetermined number n; and obtaining a motion vector predictor of the current block based on information indicating a motion vector predictor among the motion vector predictor candidates, wherein the spatial motion vector predictor candidate is obtained from neighboring blocks including a lower left block located on a lower left side of the current block, and wherein, when a first spatial motion vector predictor candidate is equal to a second spatial motion vector predictor candidate, the second spatial motion vector candidate is removed from the motion vector predictor candidates.