An apparatus for accurately determining a drowsiness level is provided. A doze prevention system includes a photographic apparatus, a drowsiness determination apparatus, and other apparatuses for doze prevention such as an alarm apparatus, a neck air conditioning apparatus, a seat belt vibrating apparatus, and a brake control apparatus. The photographic apparatus captures a facial image of a driver of a vehicle. The drowsiness determination apparatus determines a drowsiness level based on the facial image. The drowsiness determination apparatus uses a facial image captured by the photographic apparatus, detects a sign of drowsiness or a sign of struggle, and determines the drowsiness level based on the detection results.