A dual band antenna unit for a mobile device may include an antenna receiving part, a first antenna part having a first contact point and a second contact point, a second antenna part, a first feed point and a second feed point. The second antenna part may be formed integrally with the first antenna part and may extend from the first antenna part. The second antenna part may be extractably and retractably mounted in the mobile device. The first antenna part and the second antenna part may have resonant frequencies of different frequency bands. When the second antenna part is extracted, the first contact point may contact the first feed point. When the second antenna part is retracted, the second contact point may contact the second feed point. The mobile device may operate in different frequency bands using a single antenna unit, thereby allowing freedom of internal design and meeting the demand for miniaturization.