To reduce the amount of image data to be transferred while maintaining a search range even in second and subsequent search steps when a motion vector is detected using a multi-stage matching algorithm.

Image data of a composite area CA composed of areas SA indicated by a first step motion vector V1 of a macro block group selected from a frame memory 1 by a macro block selecting part 5 is read at a time, a search area of a second step motion vector V2 of each macro block is set from the image data of the composite area CA, and the second step motion vector V2 of each macro block is searched.