1. A video predictive decoding device comprising: a decoding unit which decodes side information and a compressed data of a residual signal of a target region, which is a target to be decoded, out of plural sets of compressed data obtained by encoding a plurality of divided regions; a motion information reconstruction unit which reconstructs a motion vector used to generate a predicted signal of the target region from the side information; a motion information storing unit which stores the motion vector; a motion compensation unit which generates the predicted signal of the target region, based on the motion vector; a residual signal reconstruction unit which reconstructs a reproduced residual signal of the target region from the compressed data comprising the residual signal; and a picture storing unit which adds the predicted signal to the reproduced residual signal to reconstruct a pixel signal of the target region, and which stores the reconstructed pixel signal as a previously-reproduced picture, wherein the decoding unit decodes zero-th side information and first side information, wherein the zero-th side information contains a zero-th motion vector difference, and a zero-th motion vector predictor index used to identify as a zero-th motion vector predictor one motion vector selected from a plurality of motion vectors stored in the motion information storing unit, wherein the first side information contains a first motion vector predictor index used to identify as a first motion vector predictor one motion vector selected from a plurality of motion vectors stored in the motion information storing unit, wherein the motion information reconstruction unit comprises: a zero-th motion information reconstruction unit, which derives the zero-th motion vector predictor based on the zero-th motion vector predictor index by using the one motion vector selected from the motion vectors stored in the motion information storing unit, and which adds the zero-th motion vector predictor to the zero-th motion vector difference to reconstruct a zero-th motion vector; and a first motion information reconstruction unit, which sets 0 for a vector value of a first motion vector difference, derives the first motion vector predictor based on the first motion vector predictor index by using the one motion vector selected from the motion vectors stored in the motion information storing unit, and adds the first motion vector predictor to the first motion vector difference to reconstruct a first motion vector, and wherein the motion compensation unit combines two signals acquired from the previously-reproduced picture, based on the zero-th motion vector and the first motion vector respectively, to generate the predicted signal of the target region.