In an adaptive predictive coding system for television signals in which one optimum prediction function is selected in block unit from a plurality of prediction functions alloted to a plurality of blocks each consisting of a plurality of picture elements which divide each frame for the television signal and the optimum prediction function is used for predictive coding of the television signal, a motion vector is determined in accordance with both motion vector information and prediction error information, so that the efficiency of coding can be remarkably improved especially where the transmission speed is low.