A drivers fatigue degree estimation apparatus includes a biological information value acquisition unit configured to acquire a biological information value of a driver of a vehicle, a vehicle speed detection unit configured to detect a vehicle speed of the vehicle, a stable value convergence change degree detection unit 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 and the vehicle speed, and a fatigue degree estimation unit configured to estimate a fatigue degree of the driver depending on the stable value convergence change degree.
