To immediately detect abnormal supply of electric power to a thermal head, and to stop the supply of electric power to the thermal head.

In a printing device using the thermal head in which a plurality of heat-generating resistors are arranged, a suspension period to stop the supply of electric power to the thermal head is provided at a predetermined period, during printing on a recording medium by supplying electric power to the heat-generating resistors in accordance with an input data signal. A current supplied to the thermal head is detected by a current detection unit, and the supply of electric power to the thermal head is stopped when the detected current is larger than a current threshold over a predetermined period including at least one suspension period.