An eye opening detection system that includes an imaging mechanism that captures an image of the face of a detected subject, an edge extraction mechanism that extracts the edge of the image captured, and an upper and lower eyelid detection mechanism that detects the upper and lower eyelids of the detected subject according to the edge extracted, and that detects the eye opening of the detected subject with reference to a detected distance between the upper and lower eyelids. The upper and lower eyelid detection detects the upper eyelid and detects the lower eyelid with reference to the upper eyelid detected.