1. A moving picture decoding method, comprising: dividing a target frame in a moving picture signal consisting of a temporal series of frames into a plurality of target regions; detecting motion vectors for each of the plurality of target regions with reference to a plurality of frames different from the target frame, including selecting a plurality of adjacent regions adjacent to a respective target region; identifying a motion vector of each of the selected plurality of adjacent regions; determining a predicted motion vector as the motion vector of one of the selected adjacent regions; correcting scaling of the determined predicted motion vector, by a motion vector predictor, based on all of a target reference frame referred to for detecting a motion vector of the target region, the target frame, and an adjacent reference frame referred to for detecting the motion vector of the one of the selected adjacent regions whose motion vector was used to determine the predicted motion vector; and performing decoding based on motion compensation, wherein identifying a motion vector includes referring to a first adjacent reference frame to identify the motion vector of at least one of the selected adjacent regions and referring to a second adjacent reference frame different from the first adjacent reference frame to identify the motion vector of at least another one of the selected adjacent regions.