To provide a technology that can suppress the reduction of an antenna gain while maintaining the quality of the design of the exterior furnishing of the antenna.
Provided is an antenna apparatus including: an antenna module that includes a first slot antenna that transmits or receives a first wireless signal, a first feed element that supplies power to the first slot antenna, a second slot antenna that transmits or receives a second wireless signal having a polarization direction orthogonal to a polarization direction of the first wireless signal, and a second feed element that supplies power to the second slot antenna; and a metal plate that includes a first slot, and a second slot a longitudinal direction of which is orthogonal to a longitudinal direction of the first slot.