A doping method for a semiconductor device including the following steps is provided. A substrate is provided. The substrate has a channel region. The channel region includes a first edge region, a second edge region and a center region in a channel width direction substantially perpendicular to a channel length direction, and the center region is located between the first edge region and the second edge region. A first doping process is performed on the first edge region, the second edge region and the center region by using a first conductive type dopant. A second doping process is performed on the center region by using a second conductive type dopant.