PURPOSE: To make it possible to display an excellent uniform temperature heating performance or an excellent uniform temperature cooling performance by accommodating and disposing within a vessel of the heat pipe a pipe for circulating a heat medium for carrying out heat exchange with an operating liquid for passing the heat medium from the external part and sealing the same within the vessel thereby to perform heat exchange.

CONSTITUTION: In the vessel 4 of the heat pipe 3, the upper and lower ends of the pipe are blocked by sealed flanges 4a and 4b, a heat medium passing pipe 8 penetrating through a sealed flange 4a at the upper end and curved in a hair pin shape are accommodated and disposed within a vessel. At the time of using the heat pipe, the inlet 8a and outlet 8b of a heat medium circulating pipe 8 are connected to an external heat medium supply pipeline, a heat medium for heating or cooling circulates within the pipe as shown by arrow P. For example, a plurality of heat pipes 3 are inserted into a ripening tank 2 in which a 'MISO' 1 (bean paste) is fermented from the upper part thereof. In a state where the ripening temperature within a ripening tank becomes higher than the appropriate ripening temperature by the accumulation of the fermentation heat, the heat medium of a low temperature is supplied to the heat medium circulating pipe of each heat pipe 3 via a heat medium supply pipeline 10 thereby to carry out the uniform temperature cooling of 'MISO'.