PURPOSE: To improve an information compression rate in average, by transmitting informatin by a compressing code for non-standard picture, if the transmitted screen is not the standard picture.

CONSTITUTION: The transmitted screen is supplied to a screen scanner 100, and a picture element obtained is transferred to a band compressing circuit 400 or 410 through the designation of a code switching circuit 300. After the picture signal is expanded into the compression code, the amount of information of the picture signal is compared with that of the expanded compressing code, and when the amount of the information of compression code is large, it is informed to a mode switching circuit 300 as inadequate compression to switch the mode designation, the part of a line for inadequate compression is rescanned and expanded into the compressing code again and transmitted. When the part of the line is finished, the mode is changed automatically into a mode before changeover, and the picture scanning of the next line is performed.