The present invention provides a picture coding device which reduces the amount of coded data by coding picture data using the H.264 standard. The picture coding device includes: a picture extension unit that generates an extended picture by extending an input picture using a reference value defined to be used when adjacent pixels do not exist in performing intra prediction according to the H.264standard; and a coding unit that generates a code which represents a prediction error in the extended lines with 0 by coding, using intra prediction according to the H.264 standard, the extended picture generated by the picture extension unit.