A thin fan includes a frame and a driving device disposed in the frame. The driving device includes a stator structure and a rotor structure. The stator structure includes a stator pole group and a base body connected to the frame. The stator pole group is disposed on the outer periphery of the base body. The rotor structure is disposed corresponding to the stator structure, and includes a rotor shell, a magnetic structure and an impeller connected to the rotor shell. The center of the rotor shell is formed with a cylindrical shaft, which deeply penetrates into the base body. The rotor shell and the shaft are a single component manufactured by processing a single material workpiece. The magnetic structure is disposed on the inner wall of the rotor shell, and the stator magnetic pole group magnetically drives the magnetic structure as well as the rotor shell to rotate.