A vehicle management system for handling vehicle reservations of a vehicle-sharing service includes a reservation request input device, a reservation result transmitter, and a reservation processor. When a new vehicle reservation request is input to the reservation request input device, the reservation processor performs a simple process for a vehicle allocation which allocates a vehicle to the new vehicle reservation request, and the result transmitter transmits a reservation result to a user. When the time duration after the performance of the simple process and before the rental start time for the new vehicle reservation is equal to or greater than a threshold value, the reservation processor performs an optimization process to update the vehicle allocation for the new vehicle reservation request, quickly presenting a reservation result to the user while reducing an operation cost of the vehicle-sharing service.