Provided is an inter-layer video decoding method including determining a size of a subblock of a current block by comparing at least one of a height and a width of a predetermined minimum size of the subblock with at least one of a height and a width of the current block of a first layer image; determining at least one subblock from the current block according to the size of the subblock of the current block; determining a candidate block that corresponds to the current block and is included in an encoded second layer image; determining a candidate subblock from the candidate block of the second layer image by using the subblock of the current block; determining motion information of the subblock included in the current block by using motion information of the candidate subblock included in the candidate block; and generating a prediction block of the current block by using the motion information of the subblock included in the current block.