Abstract: A driver state determination apparatus includes: an in-vehicle camera detecting a driver's sightline and head behavior; and a controller configured to determine the driver's state based on the driver's sightline and head behavior. When the driver is in an abnormal state based on the driver's sightline movement, the controller determines whether or not the driver's abnormal state a visual field impairment based on a change in each of a yaw angle and a pitch angle of the driver's head. When the abnormal state is the visual field impairment, the controller determines that the driver is aware of the visual field impairment when there is a direction in which the driver's sightline is not directed in the driver's field of view, and unaware of the visual field impairment when there is no direction in which the driver's sightline is not directed in the driver's field of view.