A moving picture prediction encoding device comprising: block division means for dividing an input image into a plurality of blocks; prediction signal generation means for generating an intra-picture prediction signal of a target block to be encoded using previously reconstructed reference samples located adjacent to the target block among the divided blocks from the block division means; residual signal generation means for generating a residual signal between the intra-picture prediction signal of the target block and a pixel signal of the target block; residual signal compression means for compressing the residual signal generated by the residual signal generation means; residual signal restoration means (108, 109) for generating a reconstructed residual signal from the compressed residual signal; encoding means for encoding the compressed residual signal; and block storage means for storing a reconstructed pixel signal of the target block to be used as reference samples, wherein the pixel signal of the target block is reconstructed by adding the intra-picture prediction signal with the reconstructed residual signal, wherein the prediction signal generation means derives reference samples from previously reconstructed blocks, stored in the block storage means, which neighbour the target block, performs an interpolation process between two or more key reference samples located at predetermined positions among the reference samples for generating interpolated reference samples, determines an intra prediction mode, and generates the intra-picture prediction signal by extrapolating the interpolated reference samples based on the determined intra prediction mode, and the encoding means encodes the intra prediction mode together with the compression data of the residual signal, and the device being characterized in that the target block has a block size of NxN samples and the key reference samples are a first key reference sample located immediately above and to the left of the upper-left sample of the target block, a second key reference sample located 2xN samples below the first key reference sample in a same vertical column as the first key reference sample, and a third key reference sample located 2xN samples to the right of the first key reference sample in a same horizontal row as the first key reference sample, and the interpolation process comprises a linear interpolation process performed on the reference samples between the first and the second key reference samples for the reference samples in the same vertical column, and between the first and the third key reference samples for the reference samples in the same horizontal row. block division means for dividing an input image into a plurality of blocks; prediction signal generation means for generating an intra-picture prediction signal of a target block to be encoded using previously reconstructed reference samples located adjacent to the target block among the divided blocks from the block division means; residual signal generation means for generating a residual signal between the intra-picture prediction signal of the target block and a pixel signal of the target block; residual signal compression means for compressing the residual signal generated by the residual signal generation means; residual signal restoration means (108, 109) for generating a reconstructed residual signal from the compressed residual signal; encoding means for encoding the compressed residual signal; and block storage means for storing a reconstructed pixel signal of the target block to be used as reference samples, wherein the pixel signal of the target block is reconstructed by adding the intra-picture prediction signal with the reconstructed residual signal, wherein the prediction signal generation means derives reference samples from previously reconstructed blocks, stored in the block storage means, which neighbour the target block, performs an interpolation process between two or more key reference samples located at predetermined positions among the reference samples for generating interpolated reference samples, determines an intra prediction mode, and generates the intra-picture prediction signal by extrapolating the interpolated reference samples based on the determined intra prediction mode, and the encoding means encodes the intra prediction mode together with the compression data of the residual signal, and the device being characterized in that the target block has a block size of NxN samples and the key reference samples are a first key reference sample located immediately above and to the left of the upper-left sample of the target block, a second key reference sample located 2xN samples below the first key reference sample in a same vertical column as the first key reference sample, and a third key reference sample located 2xN samples to the right of the first key reference sample in a same horizontal row as the first key reference sample, and the interpolation process comprises a linear interpolation process performed on the reference samples between the first and the second key reference samples for the reference samples in the same vertical column, and between the first and the third key reference samples for the reference samples in the same horizontal row.