PURPOSE: To uniformize the temperature of a head independently of the position of the heat by adjacently disposing two flow paths having the flows of a cooling liquid reverse to each other and forming a close loop as a whole right under a heating element or in the vicinity thereof.

CONSTITUTION: A heat generated by a part A is transferred by flows (a) and (b) in a body flow path part. The temperature of the flow (a) is rapidly increased at the part A and, thereafter, gradually decreased. The flow (a) is returned as the flow (b) and still lowered in temperature. When the flow (b) reaches the part A, it is rapidly heated to be raised in temperature. At this time, since the flow (a) and the flow (b) are thermally connected, the flow (a) and the flow (b) are uniformized at the average temperature of the both flows. At the time that the flow (b) is fed out of a head body 7, the temp. of the flow (b) is higher than room temp. Therefore, the flow (b) is cooled to room temp. by a heat exchange part 4, a heat release fin 5, and a fan 6, and the cooled liquid is pressurized by a pump 3 to turn to the flow (a) to be fed back again to the thermal head body 7.