A street light device includes a light emitting module, a driving circuit, a sensing module, and a microcontroller. The light emitting module includes a first light emitting unit and a second light emitting unit. The sensing module obtains a temperature, a relative humidity, and a dust concentration. The microcontroller calculates a light attenuation rate according to the temperature, the relative humidity, and the dust concentration. The microcontroller controls the driving circuit according to the light attenuation rate to drive the first light emitting unit and the second light emitting unit, so that a color temperature ratio between the first light emitting unit and the second light emitting unit is determined according to the light attenuation rate.