A thermal dissipation device for a handheld electronic device is provided. The thermal dissipation device includes a thermoelectric cooling chip, a temperature sensor, a humidity sensor, and a processing unit. The thermoelectric cooling chip has a cold surface and a hot surface. The cold surface is attached on a heating surface of the handheld electronic device by means of a heat conduction structure, and has a cold surface temperature. The temperature sensor and the humidity sensor are disposed in an area adjacent to the thermoelectric cooling chip for generating an environmental temperature and an environmental humidity respectively. The processing unit is configured to calculate a dew point temperature based on the environmental temperature and the environmental humidity; and determine whether to stop the thermoelectric cooling chip or not based on the cold surface temperature, the dew point temperature, and a heating surface temperature of the handheld electronic device.