An image processing device comprising: a decoding unit configured to decode encoded data including an initial difference coefficient that is a difference between a DC coefficient and a predetermined initial value, a replacement difference coefficient that is a difference between the DC coefficient and a (0, 0) coefficient located at the beginning of an 8×8 quantization matrix whose size is limited to be not greater than a transmission size that is the maximum size allowed in transmission, and further difference coefficients each being a difference between two adjacent coefficients in a sequence of coefficients of the 8×8 quantization matrix arranged in scan order and to set, in case a current quantization matrix is copied and a difference value between a value of identification information identifying a reference quantization matrix and a value of identification information identifying the current quantization matrix is equal to 0, a 32×32 default quantization matrix as the current quantization matrix and to set, in case the current quantization matrix is not copied, a 32×32 quantization matrix as the current quantization matrix; an inverse DPCM unit configured to set DC coefficient by adding the initial value to the initial difference coefficient and to set the 8×8 quantization matrix by setting the (0, 0) coefficient located at the beginning of the 8×8 quantization matrix by adding the DC coefficient to the replacement difference coefficient and by setting the remaining coefficients of the 8×8 quantization matrix by stepwise adding the further difference coefficients to the (0, 0) coefficient, wherein a remaining coefficient at a particular position in scan order is the sum of the (0, 0) coefficient and the difference coefficient up to said particular position; a matrix size transformation unit configured to upconvert the 8×8 quantization matrix into the 32×32 quantization matrix by performing a nearest neighbor interpolation process on matrix elements of the 8×8 quantization matrix; a replacement unit configured to replace a (0, 0) coefficient located at the beginning of the 32×32 quantization matrix set by the matrix size transformation unit with the DC coefficient set by the inverse DPCM unit; and a dequantization unit configured to dequantize quantized data obtained by decoding encoded data, using the 32×32 quantization matrix in which the (0, 0) coefficient located at the beginning has been replaced with the DC coefficient by the replacement unit or the 32×32 default quantization matrix. a decoding unit configured to decode encoded data including an initial difference coefficient that is a difference between a DC coefficient and a predetermined initial value, a replacement difference coefficient that is a difference between the DC coefficient and a (0, 0) coefficient located at the beginning of an 8×8 quantization matrix whose size is limited to be not greater than a transmission size that is the maximum size allowed in transmission, and further difference coefficients each being a difference between two adjacent coefficients in a sequence of coefficients of the 8×8 quantization matrix arranged in scan order and to set, in case a current quantization matrix is copied and a difference value between a value of identification information identifying a reference quantization matrix and a value of identification information identifying the current quantization matrix is equal to 0, a 32×32 default quantization matrix as the current quantization matrix and to set, in case the current quantization matrix is not copied, a 32×32 quantization matrix as the current quantization matrix; an inverse DPCM unit configured to set DC coefficient by adding the initial value to the initial difference coefficient and to set the 8×8 quantization matrix by setting the (0, 0) coefficient located at the beginning of the 8×8 quantization matrix by adding the DC coefficient to the replacement difference coefficient and by setting the remaining coefficients of the 8×8 quantization matrix by stepwise adding the further difference coefficients to the (0, 0) coefficient, wherein a remaining coefficient at a particular position in scan order is the sum of the (0, 0) coefficient and the difference coefficient up to said particular position; a matrix size transformation unit configured to upconvert the 8×8 quantization matrix into the 32×32 quantization matrix by performing a nearest neighbor interpolation process on matrix elements of the 8×8 quantization matrix; a replacement unit configured to replace a (0, 0) coefficient located at the beginning of the 32×32 quantization matrix set by the matrix size transformation unit with the DC coefficient set by the inverse DPCM unit; and a dequantization unit configured to dequantize quantized data obtained by decoding encoded data, using the 32×32 quantization matrix in which the (0, 0) coefficient located at the beginning has been replaced with the DC coefficient by the replacement unit or the 32×32 default quantization matrix.