1. An automatic lighting device comprising: an illuminance detector for detecting an external illuminance around a vehicle; a light controller for turning on/off a vehicular light to illuminate an outside of the vehicle, wherein the light controller turns on the vehicular light when the external illuminance is not more than an illuminance threshold; a driver's characteristics detector for acquiring information about a driver's physical characteristics; and a threshold setting element for setting the illuminance threshold in accordance with the driver's physical characteristics.