Disclosed are an antenna apparatus for a smart wearable device and a smart wearable device. The antenna apparatus for the smart wearable device includes an antenna base, a watchband electrically connected to the antenna base, an antenna body coupled to the antenna base, and a wearing posture detection circuit electrically connected to the antenna body. When the smart wearable device is worn on a user, a length formed from a tangent point between the watchband and a user's arm to a connection point between the watchband and the antenna base is a first length, and the wearing posture detection circuit is configured to determine worn posture of the smart wearable device according to the first length.