A lane departure prevention apparatus is configured to avoid lane departure even when the driver is not focused on driving operations, in a state in which the system-operating switch is OFF. The lane departure prevention apparatus has a driver condition detection section or device for detecting that the condition of the driver which is a condition in which the driver cannot perceive that the host vehicle is tending toward departure, and a lane departure avoidance control device for setting the braking control for avoiding departure in an operable state when the system-operating switch for the driver to instruct the operation of control braking for avoiding the lane departure is OFF, the braking control for avoiding departure is OFF, and the driver condition detection section or device has detected that the condition of the driver is a condition in which the driver cannot perceive that the host vehicle is tending toward departure.