A power saving method is provided. The power saving method is applicable to an electronic device including a display unit. The method comprises the steps of determining a start point on the display unit, determining whether the start point is located in a bright area of the display unit, receiving a signal corresponding to an end point on the display unit, generating a trigger signal according to the start point and the end point, and darkening the brightness of an area between the start point and the end point on the display unit according to the trigger signal.