An interlayer video decoding method and apparatus and an interlayer video encoding method and apparatus are provided. The decoding method includes: reconstructing, based on encoding information obtained from a bitstream, a first layer image and a first layer depth map; determining whether a disparity vector is predictable using peripheral blocks of a second layer current block; and when the disparity vector is not predictable using the peripheral blocks, determining a disparity vector of the second layer current block using a default disparity vector and the reconstructed first layer depth map.