PURPOSE: To remarkably enhance a print head in cooling efficiency, by a method wherein a cooling air flow generated from a centrifugal air blower driven by a two-phase stepping motor is passed through a radiator to cool the inside of the radiator.

CONSTITUTION: A drive motor 4a, which is a two-phase stepping motor, drives a centrifugal air blower 3a with a centrifugal air blowing system. Therefore, a high-speed air flow is generated from the periphery of an impeller 5a over the full radial range and over the full surface of a radiator due to the drive of the centrifugal air blower 3a either clockwise or counterclockwise. This high-speed air flow passes through an air flow path formed by radiator fins 6a, 7a, thereby discharging the heat of the radiator fins 6a, 7a outside from the radiator 2a upwards and downwards while abruptly cooling the heat. Additionally, the high-speed air flow discharged downwards results in the direct collision with a printer carriage, which fixes a print head 1a. Therefore, with the printer carriage made of a high heat-conductive material, e.g. aluminum, the heat which was transferred from the print head 1a to the printer carriage can be cooled.