In a case where it is determined that a vehicle is in an unparked state within a parking lot for at least a specified time, the parking lot where the vehicle is currently located is determined to be in a congested state, and information that pertains to the parking lot that is determined to be in a congested state is transmitted to a probe center as probe information. The probe center, based on the received probe information, creates parking lot guidance information to provide guidance on the parking lot that is in a congested state, then distributes the created parking lot guidance information to vehicles that are located in the vicinity of the parking lot that is determined to be in a congested state. A navigation device in a vehicle to which the parking lot guidance information is distributed provides guidance that pertains to the parking lot that is in a congested state.