1. An image predictive encoding device comprising: region dividing means for dividing an input image into a plurality of regions; prediction signal generating means for generating a prediction signal for an target pixel signal of a target region being a processing target out of the plurality of regions resulting from the dividing by the region dividing means; residual signal generating means for generating a residual signal between the target pixel signal and the prediction signal generated by the prediction signal generating means; and encoding means for encoding the residual signal generated by the residual signal generating means, wherein the prediction signal generating means is configured to: search a search region comprising a previously-reproduced image, for a plurality of prediction adjacent regions highly correlated to a target adjacent region consisting of a previously-reproduced adjacent pixel signal adjacent to the target region consisting of the target pixel signal; derive at least two arbitrary combinations of prediction adjacent regions including at least one of the plurality of prediction adjacent regions obtained by the search, process pixel signals of the prediction adjacent regions belonging to the derived combinations, by a predetermined synthesis method, thereby generating a comparison signal corresponding to the adjacent pixel signal for each of the derived combinations, and select a combination with a high correlation between the comparison signal and the adjacent pixel signal; and generate at least one candidate prediction signal for the target pixel signal, based on the prediction adjacent regions belonging to the selected combination, and process the candidate prediction signal by a predetermined synthesis method, thereby generating the prediction signal.