PURPOSE: To reduce the load on the software of a microprocessor.

CONSTITUTION: A serial printer has a memory 2 storing the printing data developed on a dot image, a latch circuit 5 successively latching printing dot data of one line width printed by one stroke of a printing head, a head driver 6 selectively driving the respective dots of the printing head on the basis of the printing dot data latched by the latch circuit 5 and a dot counting circuit 7 counting the number of dots to be printed from the printing dot data latched by the latch circuit 5. Further, a microprocessor 1 controlling the output of the printing data of the memory to the latch circuit 5 and determining the printing stopping time after the printing of one line corresponding to the count value obtained when the number of dots corresponding to one line is counted by the dot counting circuit is provided.