A traveling lane planning device has a processor configured to assess whether or not an approach zone exists on an adjacent lane between an event location and the current location of a vehicle, when the traveling lane plan includes a lane change from the traveling lane to the adjacent lane before the event location, to create a lane change plan in which the vehicle moves from the traveling lane to the adjacent lane after the vehicle has passed along the approach zone of the adjacent lane when it has assessed that the approach zone exists and to cause the vehicle to carry out a notification action which gives notice to the surrounding area of the vehicle that the vehicle will make a lane change from the traveling lane to the adjacent lane while the vehicle is traveling in the traveling lane along the approach zone of the adjacent lane.