In a facsimile data processing apparatus, printer code, including a line pitch amount control command and character codes are received from a host computer. The character codes are converted into image data and the image data is converted into transmission code such as modified Huffman code. The line space is directly converted into the transmission code, in the form of white code, without the conversion into image data. The line space varies according to the line pitch amount control command by changing the amount of the white code to be added.