To provide a heat radiator capable of eliminating power consumption and noise caused by a cooling fan, and also of radiating the generated heat by electronic parts efficiently without mounting a cooling fan.

The heat radiator is provided with a housing 1 which can absorb the generated heat by electronic parts 7; a phase transition element 2 which can absorb an endoergic reaction at the bottom of the housing by the phase transition between the liquid phase and the gaseous phase of a heat transfer medium; a heat dispersion element 3 which seals the upper opening of the housing and forms a phase transition space 10 of the heat transfer medium put in-between by a phase transition element 2; and a lid body for screening the heat dispersion element 3, and for consisting of an air current guide passage 6 with the heat dispersion element 3 having an opening 60 in both ends, mutually countering laterally. After decompressing the housing and impregnating the phase transition element 2 with the heat transfer medium, when the electronic parts come into contact with it, the generated heat is absorbed by the phase transition from the liquid phase to the gaseous phase of the heat transfer medium. Via the heat dispersion element 3, the heat is led to the air current guide passage from the heat transfer medium which has become the gaseous phase by the phase transition and has been filled in the phase transition space 10, so as to be eliminated via the air current guide passage 6.