In a lane boundary line recognition device, a calculation section calculates a degree of uncertainty which affects a correct recognition of white lines on a roadway of a vehicle. A learning section updates a learning value of the degree of uncertainty. A recognition suppression section suppresses execution of a recognition process of recognizing white lines on the roadway when the updated learning value is more than a threshold value. An environment change judgment section judges whether or not a road environment has changed. A learning resetting section resets the learning value of the degree of uncertainty to a previous learning value when the detection result of the environment change judgment section indicates an occurrence of change of the road environment.