A lane departure preventing device includes at least one electronic control unit. The at least one electronic control unit is configured to: when there is a likelihood that a vehicle will depart from a traveling lane, calculate a prevention yaw moment, and control a brake actuator such that the prevention yaw moment is applied to the vehicle; acquire a lateral acceleration; determine whether the lateral acceleration is greater than an ideal value by a predetermined value; control the brake actuator such that the braking force matches a target braking force required to apply the prevention yaw moment to the vehicle, when the lateral acceleration is not greater than the ideal value by the predetermined value; and control the brake actuator such that the braking force is less than the target braking force, when the lateral acceleration is greater than the ideal value by the predetermined value.