1. A communication terminal comprising: a coding part for coding a moving picture by selectively using one of an intra-coding mode and an inter-coding mode; wherein, if the intra-coding mode is used by the coding part, the coding part: calculates a difference signal by subtracting, from a first block to be coded which is in a first size and is divided from the moving picture, a prediction block in the first size generated using at least one block adjacent to the first block to be coded; divides the difference signal into a plurality of second blocks in a second size; calculates a prediction error from the difference signal based on the second blocks; compares the prediction error with a predetermined threshold; and calculates one of: (i) both a quantized AC component and a quantized DC component by executing a discrete cosine transform and quantization on the difference signal if the prediction error is greater than the threshold, and (ii) only a quantized DC component by executing the discrete cosine transform and quantization on the difference signal if the prediction error is less than or equal to the threshold.