A state monitoring apparatus in a vehicle monitors the state of a driver using a face image of the driver. The state monitoring apparatus emits light from a light projecting part toward a predetermined area and receives, via an imaging unit, light reflected by the face that is assumed to be positioned in the predetermined area. A control circuit in the state monitoring apparatus adjusts a gradation value of the face image by changing length of an exposure period in which an imaging element of the imaging unit is set to an exposure state. Further, the control circuit controls light emission of the projecting part so that light emission brightness at the time of start of the exposure period becomes higher as the exposure period of the imaging element is shortened.