Character codes having underline bits are read out of a memory (22). A character generator (18) generates character video signals in the form of horizontal scan lines corresponding to the codes. A line generator (30) generates line video signals corresponding to the underline bits. Where the apparatus is provided in a facsimile transmitter, the codes correspond to an identification of the station or the like and are entered into the memory (22) manually. Where the apparatus is provided in a facsimile receiver, the codes are received by a low speed modem (43) and stored in the memory (22). In either case, the receiver reproduces an original document in response to facsimile video signals with the identification characters, underlined where desired, superimposed on the document pattern.