A light-responsive controlling device for automatically controlling a headlamp and/or a sunshade curtain is disclosed. The control device includes a photo-sensor mounted on a vehicle for generating a sensing signal in response to the intensity of an environmental light, a discriminating circuit electrically connected to the photo-sensor for optionally generating a triggering signal according to a comparing result of the sensing signal with a reference signal, a hold circuit electrically connected to the discriminating circuit for outputting a confirming signal in response to the triggering signal uninterrupted for a predetermined period, and a drive circuit electrically connected to the hold circuit and a headlamp or a sunshade curtain of the vehicle for providing a drive current in response to the confirming signal for the headlamp to emit a certain level of light or for the sunshade curtain to perform opening/closing operations.