A window covering includes a headrail, a covering material located below the headrail, a rotating member connected to the covering material and provided in the headrail, a motor provided in the headrail and coupled to the rotating member, and a control device provided in the headrail and electrically connected to the motor. The headrail has a longitudinal direction. The rotating member is adapted to drive the covering material to expand or collapse. The motor drives the rotating member to rotate. When a moving speed of a lower end of the covering material decreases and such a situation lasts for a predetermined time, the control device controls the motor to stop operating. Whereby, no matter whether the covering material is fully expanded, fully collapsed, or encounters resistance somewhere in between, the motor can be stopped.