1. A method for detecting an upper eyelid area comprising steps of: examining an image of a vicinity of a human face photographed from the vertex to the jaws of the human face, said image including an eye, a pupil, and an upper eyelid area, measuring how brightness of the image changes with position as measured at successive positions in a given direction on the image, detecting a first position of the successive positions where the brightness of the image has decreased, detecting a second position of the successive positions where the brightness has decreased and then increased, detecting an intermediate area positioned between said first and second positions, measuring, for a plurality of sub-areas within said intermediate area, averages of values of the brightness of the image, and detecting from said intermediate area one of said sub-areas whose width is larger than the pupil's width and whose average of values of the brightness of the image in said area is lowest among said averages of values, as the upper eyelid area.