PURPOSE: To ensure that an interruption signal can be used effectively and a sheet feed and a print-out function can be controlled at a different timing using a simple software by interpreting whether the number of the first pulses and the number of the second pulses have been counted respectively based on a pulse signal which is output from a means for outputting an interruption signal.

CONSTITUTION: The subject thermal printer has ROM 2 where program data serving as a basis for processing by CPU 1 is stored, and an area for each different storage unit used when processing by CPU 1. In addition, RAM 3 where a counter for sheet feed 3a as the first counting means and a counter for printing 3b as the second counting means are formed and a communication interface 4 connected to a host computer through a circuit are connected to CPU 1 via a system bus 5. Further, the printer is equipped with a head controller 7 which controls a thermal head 6 with a dot density of 12 dots/mm and a stepping motor 8 as a drive source for transporting the sheet.