PURPOSE: To provide a heat pipe excellent in heat transfer efficiency and free from overheating, by placing boiling tips into a liquid part, in a heat pipe comprised of a pipe in which a boilable fluid is sealed, wherein a liquid part is heated from outside and a vapor part is cooled from outside.

CONSTITUTION: A liquid 2 is sealed in the pipe 1 constituting a heat pipe, the liquid-containing side, that is, the lower part of the pipe 1 is used as a heating part, while the upper part of the pipe 1 is used as a heat-radiating part, and heat is transferred from the lower to the upper part. The boiling tips 3 (pumice, zeolite, a porous sintered metal or the like) having ruggedness and a large total volume of small cavities are placed in the liquid 2. With the boiling chips 3, boiling is smoothly developed when the liquid is heated to the saturation temperature thereof by heating the lower part of the pipe 1, and the operation as the heat pipe is stabilized.