A software update system adapted to manage updating of software of a control device mounted on a vehicle, the software update system comprising: a software updating device which is mounted on the vehicle; and a server adapted to communicate with the software updating device through a network, wherein the server includes an update software distribution unit adapted to distribute update software for updating the software of the control device to the software updating device, and wherein the software updating device includes a storage device adapted to store the update software distributed from the server and adapted to store update information regarding influence on operation of the vehicle in a case where the updating of the software of the control device is not successful; and a software updating unit adapted to update the software of the control device by using the update software stored in the storage device, and adapted to control operation of the software updating unit on the basis of the update information stored in the storage device, characterized in that: the server includes an update case management unit adapted to manage the update software to be distributed by the update software distribution unit, on the basis of a processing load of the server and the update information stored in the server, and the software updating unit being adapted to determine whether or not the vehicle is movable during the updating of the software of the control device on the basis of the update information, and adapted to update the software of the control device during traveling of the vehicle in a case where it is determined that the vehicle is movable. a software updating device which is mounted on the vehicle; and a server adapted to communicate with the software updating device through a network, wherein the server includes an update software distribution unit adapted to distribute update software for updating the software of the control device to the software updating device, and wherein the software updating device includes a storage device adapted to store the update software distributed from the server and adapted to store update information regarding influence on operation of the vehicle in a case where the updating of the software of the control device is not successful; and a software updating unit adapted to update the software of the control device by using the update software stored in the storage device, and adapted to control operation of the software updating unit on the basis of the update information stored in the storage device, characterized in that: the server includes an update case management unit adapted to manage the update software to be distributed by the update software distribution unit, on the basis of a processing load of the server and the update information stored in the server, and the software updating unit being adapted to determine whether or not the vehicle is movable during the updating of the software of the control device on the basis of the update information, and adapted to update the software of the control device during traveling of the vehicle in a case where it is determined that the vehicle is movable. the server includes an update case management unit adapted to manage the update software to be distributed by the update software distribution unit, on the basis of a processing load of the server and the update information stored in the server, and the software updating unit being adapted to determine whether or not the vehicle is movable during the updating of the software of the control device on the basis of the update information, and adapted to update the software of the control device during traveling of the vehicle in a case where it is determined that the vehicle is movable.