A center includes: a storage device storing update management information including a combination of latest versions of pieces of software of first ECUs whose control functions need to be consistent with each other; and one or more processors configured to, when determining, based on the update management information and the current versions of the pieces of software of ECUs in a vehicle, that at least one of the pieces of software of the first ECUs needs to be updated, decide, as a distribution package, an one of a first difference package containing difference data between a previous version and a latest version each of all pieces of software of the first ECUs and a first total data package containing total data of the latest version of one or more pieces of software of the first ECUs that need to be updated, and transmit the distribution package to the vehicle.