Antenna device

An antenna device is provided with: a power supply element having a power supply point for supplying a signal of a first frequency band and a signal of a second frequency band lower than the first frequency band; a high-frequency band element connected to the power supply element and resonating a signal of the first frequency band; a low frequency band element connected to the power supply element and resonating a signal of the second frequency band; an auxiliary element capacitively coupled with the low-band element at the open end of the low-band element; a grounding member that is grounded; and a switch that switches between a conductive state and a non-conductive state between the grounding member and the auxiliary element. 天线装置具备：供电元件，具有提供第一频带的信号以及比第一频带低的第二频带的信号的供电点；高频带元件，与供电元件连接，第一频带的信号进行谐振；低频带元件，与供电元件连接，第二频带的信号进行谐振；辅助元件，在低频带元件的开放端，与低频带元件进行电容耦合；接地的接地构件；和开关，对接地构件与辅助元件的导通状态以及非导通状态进行切换。