A device for manufacturing an array substrate includes an exposure device for using a halftone mask to form a photoresist pattern layer on a gate insulation layer of a substrate. A polysilicon pattern layer is disposed on the substrate. A gate insulation layer covers the polysilicon pattern layer. The photoresist pattern layer includes a hollow portion corresponding to a heavily doping region of the polysilicon pattern layer, a first photoresist portion corresponding to a lightly doping region of the polysilicon pattern layer, and a second photoresist portion corresponding to an undoped region of the polysilicon pattern layer. The first photoresist portion is thinner than the second photoresist portion. A doping device is used for performing one doping process to the polysilicon pattern layer such that the heavily doping region and the lightly doping region are formed simultaneously.