A printing controller for a serial printer, wherein a carriage having a printing head is reciprocated by a motor via transmitting a means, includes a carriage position detector for detecting the position of the carriage to produce a position detection signal; a timing signal generator for detecting the rotational position of the motor, thereby producing a timing signal synchronously with the movement of the carriage in a line direction; a synchronizing signal generator for producing a synchronizing signal per each predetermined plurality of timing signal synchronously with the timing signal, and a control circuit for producing a printing initiation signal, on the basis of the position detection signal, the timing signal and the synchronizing signal, in accordance with a first timing signal after the carriage leaves a home position and receives a first synchronizing signal.