A defogging device for a surveillance camera has a heating element, a circuit board and a power cord. The heating element is mounted over the lens of the surveillance camera. The circuit board compares ambient temperature to a preset temperature, activates the heating element and has a power input terminal, a power output terminal and a temperature sensor. The temperature sensor is mounted between the power input terminal and the power output terminal and senses ambient temperature. When the ambient temperature is above the preset temperature, the circuit board activates the heating element. The power cord is connected to the circuit board and the heating element and transmits power to the heating element from the circuit board. By activating the heating element during periods of cold ambient temperature, the defogging device removes fog and frost from or keeps fog and frost from forming on the lens of the surveillance camera.