In detecting a motion vector, sub-sampling is more selectively and adaptively set in terms of power consumption and detection performance. A correlation calculation section includes a plurality of correlation calculation blocks, each calculating correlation between a block to be coded and an associated candidate block within a search range. Each correlation calculation block is supplied with a different group of pixels of the block to be coded and an associated group of pixels of the associated candidate block, and calculates the correlation between the two groups of pixels supplied. A control section selectively sets sub-sampling in accordance with image feature information such as the frequency components of the block to be coded or operating state information such as the power left in a battery. And, in accordance with the setting of sub-sampling, the control section selectively operates part or all of the correlation calculation blocks of the correlation calculation section.