A moving picture coding device according to the present invention includes: a QP deriving unit which derives, based on a moving picture signal, a quantization step and a small quantization step having a size smaller than a size of the quantization step; a small QP position determining unit which determines a position, within a picture, of a first block group to be quantized by using the small quantization step; and a video encoder which quantizes the first block group at the determined position by using the small quantization step and a second block group at a position within the picture other than the position of the first block group by using the quantization step.