There is provided an elevator group control system, in which even after an assigned car has been determined, the assigned car can be changed as necessary, and therefore comfortable service can be offered to a user. This group control system includes a call registration device by the use of which a user registers a hall destination call before getting into a car, a car position detection part for detecting the car position of each elevator, and a call registration storage part for storing, for each elevator, a hall destination call having been registered. When a hall destination call having the same contents as those of an already registered hall destination call stored in the call registration storage part is registered newly from the call registration device, if a non-assigned car has already arrived at the floor on which the call registration device is installed, the newly registered hall destination call is assigned to the non-assigned car.