PURPOSE: To enable adjustment to all dot densities, by coupling a print head rotatably to the rotary shaft of a motor arranged on a carrier, and providing an electrical circuit for controlling the motion of the print head and the motor.

CONSTITUTION: A motor 2 is mounted on the rear portion of a carrier 5 while a print head 4 is secured to a shaft 3 coupled to the motor 2 and separated from the carrier 5. When the motor 2 is driven, the print head 4 can be rotated on the shaft 3. Furthermore, an electrical circuit (firmware) for controlling the motor 2 and the print head 4 is connected through wires 7a, 7b to the motor 2 and the print head 4. Since the print head 4 is rotated around an axis normal to the print face and the rotary amount is controlled by the firmware, the dot density in the longitudinal direction can be varied freely thereby the dot density at the printer side can be matched freely to the dot density specified by a host device.