A plurality of lighting units are positioned forwardly of the driver seat in the cabin of a vehicle for applying infrared radiations in respective directions to the vehicle driver seated on the driver seat. The intensities of the emitted infrared radiations are controlled according to respective basic controlled variables depending on the illuminance in the vehicle cabin. The position and orientation of the face of the vehicle driver are recognized from an image captured of the vehicle driver by an imaging device, and the basic controlled variables are corrected according to the recognized position and orientation, thereby adjusting the intensities of the infrared radiations emitted from the lighting units and a balance of the infrared radiations emitted from the lighting units. Thereafter, the illuminance in the vehicle cabin and the recognized position and orientation change, then corrective coefficients for the basic controlled variables are updated depending on the changes.