A drivers fatigue degree estimation apparatus includes a biological information value acquisition unit (2) configured to acquire a biological information value indicative of biological information of a driver of a vehicle, a vehicle speed detection unit (4) configured to detect a vehicle speed of the vehicle, a stable value convergence change degree detection unit (20) configured to detect a stable value convergence change degree which is a degree of change in the biological information value from a peak value of the biological information value increasing after the vehicle starts deceleration compared to the biological information value before the vehicle starts the deceleration, to a preset stable value, to which the biological information value decreases after the vehicle stops, based on the biological information value acquired by the biological information value acquisition unit (2) and the vehicle speed detected by the vehicle speed detection unit (4), and a fatigue degree estimation unit (22) configured to estimate a fatigue degree of the driver depending on the stable value convergence change degree detected by the stable value convergence change degree detection unit (20) .
