PURPOSE: To reduce the number of calculation times for a degree of correlation to detect a motion vector by selecting detected motion vectors as candidates and calculating the degree of correlation of plural block positions indicated by those candidate motion vectors.

CONSTITUTION: Motion vector memory 14 which receives motion vector information 41-45 outputted from motion vector detectors FIVD1-4 and FRVD1 stores them once. When candidate motion vector information 17 is sent from each of the detectors FIVD1-4 and FRVD1 to a motion vector selector/expander 15, the selector/expander 15 reads out a required motion vector from the memory 14 as motion vector information 16, and outputs it as the candidate motion vector information 17, and supplies it to a requesting detector. Field block readers FIBR1-4 and a frame block reader FRBR1 read out image signals 31-35 from image memory 20 according to the information 41-45, and output a prediction signal 13 via switches 61, 62 and a prediction signal output device 70.