A printed wiring board includes an insulation layer having a first penetrating hole penetrating through the insulation layer, a magnetic core structure including a magnetic material filled in the first penetrating hole through the insulation layer such that the magnetic core structure including a first magnetic body layer formed in the first penetrating hole is formed through the insulation layer, and a conductor layer formed on the insulation layer and having an inductor pattern such that the inductor pattern is surrounding a circumference of the magnetic core structure. The magnetic core structure and the inductor pattern of the conductor layer form an inductor device.