A double-deck elevator group controller which controls the operation of a plurality of cars of an elevator system having cars vertically connected to each other in the same shaft, comprising: a hall-installed destination floor input device which is installed in a hall of each floor, by use of which a passenger registers a from-hall car call by inputting his or her destination floor; operation mode storage means which stores, for each car of a plurality of connected cars, two operation modes: a first operation mode in which an upper car of the connected cars serves an upper lobby floor and even-numbered service floors and a lower car of the connected cars serves a lower lobby floor and odd-numbered service floors and a second operation mode in which the upper car and lower car of the connected cars serve all floors at which the cars can stop; and from-hall car-call assigned candidate car selection means which, upon registration of a from-hall car call by the hall-installed destination floor input device, regards a car whose operation mode is the first operation mode as an assigned candidate car for the from-hall car call when a combination of boarding and alighting floors of the from-hall car call corresponds to any one of operation between an upper lobby floor and an even-numbered service floor, operation between an even-numbered service floor and an even-numbered service floor, operation between a lower lobby floor and an odd-numbered service floor and operation between an odd-numbered service floor and an odd-numbered service floor and a minimum value of an increment of the number of stops obtained when the from-hall car call is assigned to a car of the first operation mode is not more than a minimum value of an increment of the number of stops obtained when the from-hall car call is assigned to a car of the second operation mode. a hall-installed destination floor input device which is installed in a hall of each floor, by use of which a passenger registers a from-hall car call by inputting his or her destination floor; operation mode storage means which stores, for each car of a plurality of connected cars, two operation modes: a first operation mode in which an upper car of the connected cars serves an upper lobby floor and even-numbered service floors and a lower car of the connected cars serves a lower lobby floor and odd-numbered service floors and a second operation mode in which the upper car and lower car of the connected cars serve all floors at which the cars can stop; and from-hall car-call assigned candidate car selection means which, upon registration of a from-hall car call by the hall-installed destination floor input device, regards a car whose operation mode is the first operation mode as an assigned candidate car for the from-hall car call when a combination of boarding and alighting floors of the from-hall car call corresponds to any one of operation between an upper lobby floor and an even-numbered service floor, operation between an even-numbered service floor and an even-numbered service floor, operation between a lower lobby floor and an odd-numbered service floor and operation between an odd-numbered service floor and an odd-numbered service floor and a minimum value of an increment of the number of stops obtained when the from-hall car call is assigned to a car of the first operation mode is not more than a minimum value of an increment of the number of stops obtained when the from-hall car call is assigned to a car of the second operation mode.