An antenna unit and an antenna device are provided. The antenna unit comprises a first substrate, a signal line, a first electrode, a second electrode, and an auxiliary electrode. The first substrate has a first surface and a second surface opposite to the first surface. The signal line is located on the first surface of the first substrate. The first electrode is located on the second surface of the first substrate. The first electrode is overlapped with the signal line. The first electrode is ring-shape. The second electrode has a through hole. An accommodating space of the through hole is overlapped with the first electrode. The auxiliary electrode is overlapped with the accommodating space of the through hole and the first electrode.