A tunable antenna device includes a substrate, a switch, a control circuit, an antenna and a frequency adjustment portion. The substrate includes first and second surfaces and first and second through-holes. The switch is on the first surface and includes first, second and first control terminals. The control circuit is on the first surface and electrically coupled to the first control terminal. The antenna is on the second surface and includes first and second radiation members. The frequency adjustment portion is on the second surface and includes first and second metal portions. The first metal portion includes a first interdigital structure electrically coupled to the first radiation member. The second metal portion includes second and third interdigital structures electrically coupled to the second radiation member. The second and third interdigital structures are electrically coupled to the first and second terminals through the first and second through-holes respectively.