PURPOSE: To prevent the lowering of the circulating function of a refrigerant due to the interference of a steam current and a condensed liquid by mounting a guide plate to the lower gaseous-phase chamber of a condenser and separating the passages of the gaseous phase and the liquid phase.

CONSTITUTION: The refrigerant 3 enters into the sealed vessel 2 of a boiling section 1, and a heating element 4 is immersed into the refrigerant 3. A condensing section 5 connected to the sealed vessel 2 is mounted to the upper section of the boiling section 1. A large number of refrigerant passages 12 are formed to the condensing section 5, and these upper ends are opened to an upper gaseous-phase chamber 10 and these lower ends to the lower gaseous-phase chamber 11 respectively. The guide plate 13 is mounted slantingly into the lower gaseous-phase chamber 11. The upper end of the guide plate 13 contacts with the inlet section of the lower end of a gaseous-phase refrigerant passage 12', and the guide plate introduces the steam current of a gaseous-phase refrigerant 8. Some clearance is formed between a lower end and the wall of the lower gaseous-phase chamber in the lower end so that a liquid-phase refrigerant 9 as the condensed liquid can fall to the boiling section.