PROBLEM TO BE SOLVED: To provide a drivers undrivable state detector capable of highly accurately detecting that a driver is in an undrivable state.SOLUTION: A drivers undrivable state detector comprises: facial-direction detection means directing a direction of a drivers face with respect to a front of a vehicle 10 on the basis of a driver seat image picked up by a driver camera 21 mounted in a vehicle 10 and facial-direction off-balance state detection means detecting that the driver is in an undrivable state if the direction of the drivers face detected by the facial-direction detection means is greater than a facial-direction threshold for time longer than facial-direction off-balance determination time during the running of the vehicle 10.
