An automatic driving system for an automatically driven vehicle. In the system, a travel direction acquirer is configured to acquire travel direction information that is information indicative of whether or not each of lanes in a parking lot is unidirectional. In addition, in the system, an allowance determination unit is configured to, if determining, based on the travel direction information acquired by the travel direction acquirer, that each of the lanes in the parking lot is unidirectional, allow automatic driving of the automatically driven vehicle.