PURPOSE: To perform current control in accordance with printing duty, thereby improve printing density by chopping a coil current according to the amount of printing data after the lapse of a current increasing time.

CONSTITUTION: When printing data 5 is provided, it is loaded into a dot line buffer 7 by means of a clock signal 6 in synchronization with printing data 5. After this, a pulse signal regulated by times T1, T2 which are set by a current increasing time T1 setting part 8 and a current application time T2 setting part 10 is entered into a printing head drive circuit 11, synchronized to printing timing through a data gating circuit 9. Then the current is caused to run through a deenergization coil (printing coil) 11, which in turn releases a printing hammer for printing. At that time, the amount of printing data 5 is detected by a detection circuit 12 and this detection signal is entered into a t3/t4 time setting part 13. Next, an output signal from the setting part 13 is supplied to an OR gate 14, and after the lapse of a current increasing time T2, a chopping current/corresponding to the amount of printing data is caused to pass through the coil 11. In this way, printing is performed without density unevenness.