PURPOSE: To prevent the omission of words or the lack of characters by inputting a previously set up print code to a printing control circuit to actuate the printing control circuit and checking its output data.

CONSTITUTION: A video signal inhibition from a microcomputer 5 is turned to logical L during printing between pages to inhibit the sending of a video signal to a laser beam printer. Subsequently, the previously set up print code is inputted to the printing control circuit 3. When the existence of a printing start signal is detected, the circuit 3 starts to operate and outputs a video signal. The video signal is inputted to a serial/parallel converter 6 and converted into parallel data. The computer 5 reads out the parallel data from a data bus and checks whether the parallel data are correct or not as compared to the set up print code. Thus, the omission of words or the lack of characters can be prevented, so that the reliability of the printing control device can be improved.