A picture coded signal decoding apparatus for decoding a plurality of picture coded signals into one picture signal. The apparatus includes a code string editing unit which edits the picture coded signals to generate one picture coded signal, and a decoder which decodes the one picture coded signal to generate one picture signal. The code string editing unit generates the one picture signal representing a composite picture including pictures corresponding to said picture coded signals. Each picture coded signal includes at least one coded sub-picture representing a sub-picture having a predetermined number of scanning lines. Each coded sub-picture includes a positional code for indicating a sequential position of the sub-picture in the picture coded signal. The code string editing unit includes an extracting unit which extracts the coded sub-picture included in each picture coded signals from each the picture coded signal, a connection unit which connects the extracted coded sub-pictures in a predetermined sequence, and a numbering unit which changes the positional codes at sequential positions according to a predetermined rule.