A multi-coil inductor includes a plurality of stacked inductor units. Each of the inductor units comprises: a magnetic core in which a magnetic path is formed; and a plurality of coils which are wound around the magnetic core to form at least one winding pair. Wherein a part of the magnetic path between the adjacent inductor units is shared. In the present invention, the leakage inductance is controlled and the maybe magnetic saturation of magnetic core avoided by adjusting series and parallel connections among the coils.