A traveling condition determination device for use in a vehicle includes an imaging unit for periodically capturing an image of a road on which the vehicle is traveling, a recognition unit for recognizing a marker on a side of the road relative to the vehicle, a detection unit for detecting an angle of the vehicle relative to the marker recognized by the recognition unit, a storage unit for storing the angle of the vehicle detected by the detection unit in an analyzable manner and a determination unit for determining a traveling condition of the vehicle based on the angle stored in the storage unit.