An antenna device for radio communications in a wearable device comprises a ground plate having an arc shape, a first antenna plate extending essentially parallel to the ground plate and connected thereto at a first end portion of the ground plate, the first antenna plate having a first feed terminal, and a second antenna plate extending essentially parallel to a the ground plate and connected thereto at a second end portion of the ground plate opposite to the first end portion of the ground plate, the second antenna plate having a second feed terminal. A gap is provided between the first antenna plate and the second antenna plate.