In an antenna device, first linear portions of a coil conductor are located on a lower surface of a first resin sheet. Second linear portions of the coil conductor are located on an upper surface of a second resin sheet. Via conductors of the coil conductor are formed in the first and second resin sheets and intermediate resin sheets located between the first and second resin sheets. The via conductors connect a first end and a second end of the first linear portions and a first end and a second end of the second linear portions, respectively. The first and second linear portions and the via conductors define the coil conductor. Each of the intermediate resin sheets includes an aperture in the center portion thereof. The lamination of the apertures defines a cavity in which a magnetic substance core is embedded. The coil conductor is wound around a periphery of the cavity.