A fatigue degree determination device includes a fatigue degree determination unit. A first biological heart rate is acquired while a user is awake and at rest, based on a biological heart rate measured from the user. A second biological heart rate is acquired while the user is sleeping, based on the biological heart rate measured from the user. The fatigue degree determination unit determines a fatigue degree of the user, based on information read out from a storage medium, the first biological heart rate and the second biological heart rate. The storage medium stores the information in which a degree of change of one biological heart rate relative to the other biological heart rate of a biological heart rate while a person is awake and at rest and a biological heart rate while the person is sleeping and a fatigue degree are associated with each other.