Abstract: In a serial impact printer, a printing head having an impact wire pin array of two arrangement lines is mounted on a carriage in such a way that the pin arrangement lines are inclined by an angle .theta. with respect to the virtual vertical direction. The respective wire pins in the array are driven at timings different delay time by delay time according to the inclination angle .theta.. The control circuit for determining the drive timings comprises a circuit for turning on the respective wire pins at the delay time intervals and a circuit for turning off the respective wire pins in sequence at the delay time intervals after a predetermined time has elapsed. It is desirable that the inclination angle .theta. satisfies the following formula:tan .theta..ltoreq.a/(2.multidot.b)where 2a denotes the pitch between two adjacent wire pins arranged along a single arrangement line of the array, and b denotes a distance between the two arrangement lines of the array.