1. An information processing apparatus comprising: an input unit configured to input an image; a face detection unit configured to detect a face of a person from the image input from said input unit; a first calculation unit configured to calculate a feature amount associated with an eye open/closed state from the face detected by said face detection unit; a second calculation unit configured to calculate, as a feature-change amount, a difference between the feature amount calculated by said first calculation unit and a feature amount calculated from a face detected from an image input before a predetermined time; a third calculation unit configured to calculate an eye open/closed degree of eyes of the face detected by said face detection unit on the basis of the feature amount and the feature-change amount; and a weighting unit configured to set weights for the feature amount calculated by said first calculation unit and the feature-change amount calculated by said second calculation unit, wherein said third calculation unit calculates the eye open/closed degree of eyes of the face detected by said face detection unit on the basis of the feature amount and the feature-change amount for which said weighting unit sets the weights wherein said first calculation unit calculates a feature amount associated with an eye open/closed state of a person from faces of the person that are detected from a plurality of images input from said input unit within a predetermined time, and wherein said third calculation unit calculates the eye open/closed degree of eyes of the face detected by said face detection unit on the basis of only the weighted feature amount when a difference between a maximum value and a minimum value in a plurality of feature amounts calculated by said first calculation unit from the plurality of images has a predetermined relation with a preset threshold.