Abstract: A system for preventing abnormal heating of a thermal head, which is configured with pure hardware. In the system, when a temperature of the thermal head becomes an abnormally high temperature exceeding a predetermined temperature and/or an active time of a print-time setting signal cyclically issued from a microcomputer for activating the thermal head only for a time period necessary for printing of one line of picture image becomes abnormally long, a flip-flop is set so that three sorts of switch circuits are respectively operated in such a manner as follows, whereby the abnormal heating of the thermal head can be prevented at a very high reliability.(1) The supply of a drive voltage to the thermal head for heating the thermal head is forcibly stopped.(2) The input of the print-time setting signal to the thermal head is forcibly stopped.