PROBLEM TO BE SOLVED: To provide an instrument for estimating sleepiness which permits sleepiness to be more accurately estimated and a method for estimating sleepiness.SOLUTION: In the sleepiness estimating instrument 10, a closed-eyes and opened-eyes decision section 15 detects an opened-eyes condition and a closed-eyes condition based on the degree of opening of the eyes and computes time Tclose required for the change from the opened-eyes condition to the closed-eyes condition and time Topen required for the change from the closed-eyes condition to the opened-eyes condition. An erroneous detection section estimation section 16 decides that the opening and closing action of the eyes is a blink at the time when the relation of Tclose≤Topen is satisfied. Furthermore, only the feature amount of the blink of the opening and closing actions, when the erroneous detection section estimation section 16 decides that the actions are the blink, is used for estimation of sleepiness by a sleepiness estimation section 18. Thus by deciding about the blink by Tclose and Topen based on the degree of opening of the eyes, the instrument effectively reduces the erroneous detection of the blink at the time of sleepiness estimation.
