An exemplary building sway operation system (10) for an elevator includes an acceleration sensor (11), and a data receiving unit (12) for receiving a sensor output from the acceleration sensor (11). The acceleration sensor (11) is designed to be mounted on a movable mass (6) of an active vibration control device (5) for a building, in order to detect the reciprocating motion of the movable mass (6) of the active vibration control device (5) responsive to the occurrence of earthquakes or strong winds.