An antenna apparatus and a terminal device are provided, which relate to the field of communications technologies. A switch disposed at an end of an antenna arm controls an antenna to switch to different resonance frequencies, therefore reduced antenna efficiency caused by switch loss is avoided and space occupied by the antenna is not increased. The antenna apparatus includes an antenna and a printed circuit board, where a feedpoint and a first grounding point are disposed on the printed circuit board, the antenna is connected to the feedpoint, and the antenna includes a first arm.