A position sensor includes a variable capacitor assembly and a circuit board. The variable capacitor assembly includes a baseboard and a dielectric coupling element. The baseboard includes a baseboard body, a grounding electrode and two power electrodes. The grounding electrode is disposed nearby one side of the baseboard body. The two power electrodes are disposed separately near the other side of the baseboard body. The dielectric coupling element is spaced with the two power electrodes and the grounding electrode, and operable to be moved along a moving path. A covering condition is varied when the dielectric coupling element is operated to move along the moving path. When a power is alternatively applied to the power electrodes, a pair of capacitance values between the grounding electrode and the power electrodes is varied with the covering condition to accordingly determine a relative position of the coupling element along the moving path.