A system for commonly utilizing a vehicle in which illegal use of the vehicle can be surely prevented. In the system for lending a shared vehicle, which is parked in a parking area and of which the use information concerning lending and returning is managed, to a user after confirming permission to utilize the vehicle based on previously registered personal identification information, the shared vehicle is provided in the control section thereof with a popup key which can control whether a mechanical switch unit for starting the driving of the vehicle can be operated or not, and with an ignition mechanism control mean which permits starting operation of an ignition mechanism when personal cipher information inputted by the user matches personal cipher information imparted to the user in association with the personal identification information and the user sets a destination, and permits returning operation of the ignition mechanism when arrival at the set destination is detected.