A moving image encoding and decoding system may include a moving image encoding device and a moving image decoding device that provides motion vector prediction and encoding of a difference motion vector even when a block serving as a candidate of motion vector prediction does not have significant motion information. The moving image encoding device 100 includes a motion vector predictor 114 that may select a first region from already encoded regions stored in a frame memory 104. When, for example, the selected region does not have a reference frame number, the moving image encoding device can search for and select a second region having a determined level of correlation with a template region. The template region is composed of pixel signals already reproduced from a reference image specified with a reference frame number associated with a target region. The moving image encoding device 100 may produce a prediction motion vector based on the spatial positional relationship between the target region and the selected first or second region. Using the prediction motion vector, a difference motion vector can be calculated.