The invention relates to an elevator apparatus, comprising: a shaft, an elevator car vertically movable in the shaft, one or more ropes connected with the car, and a controller for controlling movement of the car. In order to detect sway in one or more elevator ropes connected with the car, the apparatus comprises at least one sensor unit arranged in the elevator shaft to detect sway and to produce a control signal indicating to the controller the detected sway. The controller compares the detected sway to a predetermined limit and prevents movement of the elevator car when sway reaches the predetermined limit.