An image compression method and apparatus, in which coding efficiency is improved by coding multiple pictures through cross-reference between the pictures, and an image decompression method and apparatus. The image compression method includes dividing each of the pictures into predetermined slices, determining a prediction mode having higher efficiency and a coding order for each of corresponding slices of the pictures by performing prediction on the corresponding slices, and coding each of the slices in the determined prediction mode according to the determined order of coding. The pictures are coded through cross-reference between them.