An elevator rope sway detection method and a detection device using the same capable of detecting an elevator rope sway, generated by a building shake caused by an earthquake or strong wind, with high accuracy by preventing incorrect detections in detecting the elevator rope sway. A rope detector including a rope sway detector sends detection information detected by the rope detector to a rope determiner. A rope sway determination mechanism includes a detection signal memorization unit, a detection signal calculation unit, and a rope sway determination unit to determine that a rope sway occurs if the detection information sent from the rope detector fulfills a predetermined condition. A result determined by the rope sway determination unit is sent to an elevator controller, which performs an operation corresponding to the determined result.