An inductor structure including a first winding turn and a second winding turn is provided. The first winding turn is disposed above a substrate. The second winding turn is disposed between the first winding turn and the substrate. One end of the second winding turn is grounded, and the other end of the second winding turn and the first winding turn are electrically connected in series. The first winding turn and the second winding turn form a three-dimensional helix structure above the substrate. The width of the second winding turn is greater than that of the first winding turn, and furthermore, the first winding turn is projected onto the second winding turn.