An inductor includes a core substrate including minute column-like electrical conductors extending between a front surface and a back surface of the core substrate. Each column-like electrical conductor is insulated from adjacent column-like electrical conductors by being surrounded by an insulating material. Insulation layers are formed on the front surface and the back surface of the core substrate, respectively. At least two connection electrical conductors extend through each of the insulation layers. Each connection electrical conductor is electrically connected to a plurality of the column-like electrical conductors. Wirings are formed on each of the insulation layers to connect said connection electrical conductors to each other electrically. The wirings, the connection electrical conductors and the column-like electrical conductors are connected to form a coil in a three-dimensional manner.