PURPOSE: To save surplus energy and contrive a reduction in printing noise, by controlling an exciting current for a printing head according to a value of the set number of sheets to be printed in an overlapped state.

CONSTITUTION: Normally a controlling part 1 controls a printing head 3 and a printing mechanism 4 to perform printing. An exciting current supplied to the printing head 3 is controlled to a predetermined value so as to obtain a required impact force according to the setting of a switch 2 for setting the number of sheets to be simultaneously printed, by the controlling part 1. Thus, the exciting current supplied to the printing head can be controlled to an appropriate value according to the number of sheets to be simultaneously printed in an overlapped state, so that it is possible to save otherwise wasted energy when the number of the sheets to be simultaneously printed is small. In addition, a reduction in printing noise can be contrived.