PURPOSE: To prevent a fall of service function of an elevator and smoothly bring back the transmission to its normal state, even if abnormality occurs in signal transmission between the group supervisory operation control device of the elevator and the elevator control device.

CONSTITUTION: When any abnormality occurs in transmission between a group supervisory operation control device 3 and an elevator control device 5, the output destination of the transmission signals of landing remote stations 9A-9N is changed from the main station 1 of the group supervisory operation control device to the main station 2 of the elevator control device. Further, after the changeover, the timing of changeover of the output destination of the transmission signals of the landing remote stations 9A-9N to the main station 1 is controlled by a transmission passage changeover timing control means 8.