An antenna unit includes an antenna body having a fed radiation electrode
and a non-fed radiation electrode that generate a double resonance state
and that are mounted on a dielectric substrate, and a substrate for
mounting the antenna body thereon. A ground electrode is disposed on the
substrate in a predetermined area other than a ground-electrodeless
portion provided on the substrate. The ground-electrodeless portion
extends from at least one portion of an antenna-body mounting area so as
to extend off of and away from the antenna-body mounting area. Grounding
ends of the fed radiation electrode and the non-fed radiation electrode
are connected to the ground electrode via grounding lines disposed on a
predetermined portion of the ground-electrodeless portion, the
predetermined portion being outside the antenna-body mounting area.
