There is provided a dewfall preventing device of a refrigerator for preventing dew from forming on the contact portion of a refrigerator case and a door, the device comprising a heat exchanger for concentrating the waste heat generated from a compressor with contacted to the compressor of the refrigerator and a thermosyphon, its two ends connected to the heat exchanger, and having a working fluid phase-transferred into a gas phase after heat-exchanging with the waste heat from the compressor, move along the hot line, vaporize the dew forming on the contact portion of a refrigerator case and a door by the radiation of the heat, transferred into a liquid phase, fallen down by gravitation, and introduced back into the heat exchanger.