PURPOSE: To provide a serial printer preventing the lowering of printing quality due to interruption processing without adding a latch circuit.

CONSTITUTION: A serial printer is equipped with a printing mechanism 83 to which a current is supplied corresponding to printing data, a time setting means (timers B1, B2) setting the current supply time to the printing mechanism and a control means (CPU 61) prohibiting interruption processing before the time set by the time setting means is completed.