Compression method of interlace moving image signals

A compression method for moving picture signals that are interlace moving pictures, when prediction coding is used as the method of compressing image signals, divides an input frame image into input field images, divides a comparison frame image into comparison field images, detects a motion vector of the input field image with respect to those comparison field images, and makes an extracted motion vector which is smaller than the value for evalution of prediction error, the motion vector for motion compensation prediction coding. In addition, a reference frame is set for each predetermined inter-frame interval, and the field image signals of one of the reference frame image signals have intra-field coding performed by linking inside fields, while the other of the field image signals undergoes inter-field coding on the basis of signals that have undergone coding processing for the other field image signal or the image signals of it, while the other frame image signal undergoes inter-frame coding on the basis of field image signals corresponding to the reference frame that comes either before or after it, or those signals that have undergone coding processing.