A high-efficiency coding apparatus is provided which can increase accuracy in motion compensation and also increase processing speed without increasing the circuit scale as compared with the case that motion detection is carried out with respect to both of even and odd fields. Thus, this high-efficiency coding apparatus can perform accurate encoding, and can realize satisfactory transmission or recording of information. This high-efficiency coding apparatus is formed with frame memories for storing image information of a present frame therein, a frame memory for storing image information of a preceding frame therein, a frame type/2-field type motion detecting circuit for obtaining frame motion vector data of half-pel accuracy and 2-field motion vector data of half-pel accuracy by effecting motion detection of pixel data located within reference blocks located within the search area of a preceding frame and pixel data located within a remarkable block of the present frame, and selectively outputting these motion vector data. A motion compensating circuit effects motion compensation based on the selected output and an adding circuit effects encoding of the image information of the present frame and motion-compensated image information.