An absentminded state determination apparatus includes: a data obtaining element for obtaining a time series data of a physiological characteristic value of a participant, wherein a fluctuation component is overlapped on the time series data, and depends on a state of the participant including normal and absentminded states； a detection element for detecting reflecting portions of the time series data, which reflect on the fluctuation component； a counting element for counting the number of the reflecting portions of the time series data in a determination time period between a determination time and a certain past time； and a determination element for determining according to the number of the reflecting portions at the determination time whether the participant is in the absentminded state. The determination time period has a predetermined time width from the certain past time to the determination time.
