The present invention provides a cord controller to be mounted on a top rail of a window covering. The cord controller includes a base, a cord controlling device, and a cord regulating device. The base has a chamber therein and an inlet and an outlet on opposite sides of the chamber, and the cord controlling device and the cord regulating device are received in the chamber. The cord controlling device has a gap between the inlet and the outlet for the cord to pass through. The cord regulating device is adjacent to the outlet and has cord pressing bar to form a passageway between the cord pressing bar and the base for the cord to pass through. Therefore, the cord controller may avoid the cords twisting and keep a smooth movement of the cords.