Method and apparatus for encoding/decoding image efficiently

A method for encoding/decoding an image efficiently and an apparatus thereof are provided to calculate a motion vector of a main reference image, and induce an assistant reference image from the motion vector. An entropy encoder(201) restores integer values, corresponding to the quantization result of residual images between the current image and an estimated image, and the encoding data of the current image. A reverse quantization unit(202) restores frequency coefficients of the residual images. An inverting unit(203) restores the residual image.