In an elevator system in which a plurality of cars are operated in a coupled or independent manner in a single hoistway, an elevator group-control device includes a front-car car-call detection unit detecting a car call of a front car with respect to its traveling direction out of the plurality of cars or for detecting a floor and a car that are assigned a destination floor of a registered destination floor call; and a rear-car assignment-candidate exclusion unit excluding, from assignment candidate cars, a rear car in the same hoistway as the front car assigned the car call when a landing call for the same direction as the traveling direction is registered at a floor registered by the car call detected by the front-car car-call detection unit.