To provide the stable starting and stable operation of a variable conductance heat pipe irrespective of a situation in preservation, transportation, and installation.

In the variable conductance heat pipe, a working fluid and a non-condensible gas are sealed in an airtight container 1 extended in an axial direction, a heating source 9 is attached to one side of the airtight container 1, and a cold source 10 is attached to the other side. The pipe is composed so that a portion 15 with more favorable water conductivity than other portions is provided at one part of a cross section perpendicular to an axis of the airtight container 1, and the portion with favorable water conductivity is extended in the axial direction.