A fan comprises a fan frame, a motor, an impeller, a circuit board and an enclosing layer. The fan frame has a motor base disposed in a central portion thereof. The motor is mounted on the motor base and has a rotor, a stator and a bearing unit. The stator is disposed around the outer periphery of the bearing unit, and the rotor is sheathed on the stator and the bearing unit. The impeller is mounted on the motor. The circuit board is sheathed on the bearing unit and located between the stator and the motor base, and has a plurality of electronic components disposed on a first surface thereof. The stator and the circuit board are enclosed by the enclosing layer, and the plurality of electronic components are enclosed by the uniform enclosing layer with a specific thickness.