A lane keeping assist apparatus is disclosed which includes a lane detecting part; an information output device; an actuator that generates a force for changing an orientation of a vehicle; and a controller that performs a lane keeping assist control based on a positional relationship between the lane and the vehicle, wherein the lane keeping assist control includes an alert control and an intervention control via the actuator, the controller selectively operates in a first mode where the alert control and the intervention control are executable, a second mode where only the intervention control is suppressed or a third mode where the alert control and the intervention control are suppressed, and the controller, during operating in the first mode, performs a mode transition to the second mode when the abnormality determination results indicate an abnormal state concerning only the part related to the intervention control.