SOFTWARE UPDATE SYSTEM, SOFTWARE UPDATE DEVICE, SOFTWARE UPDATE METHOD, AND STORAGE MEDIUM

A software update system including a vehicle and a server device configured to communicate with the vehicle via a network includes an update control unit configured to execute a software update process for an electronic control unit provided in the vehicle by using a new version of software supplied from the server device via the network, and an occupant detection unit configured to detect an occupant left behind in a seat of the vehicle, wherein the update control unit restricts the software update process in a case where the occupant detection unit detects the occupant left behind.