Antenna apparatus and module apparatus

[Object] To provide an antenna apparatus which can allow a user to freely select service which utilizes the electromagnetic field communication technology. [Solution] Provided is an antenna apparatus including: a first antenna configured to generate a magnetic field by flow of a current; and a module unit including a second antenna whose opening area is smaller than an opening area of the first antenna and which is able to be electromagnetically coupled with the first antenna, and a module configured to operate by a current generated by the second antenna through electromagnetic coupling between the first antenna and the second antenna. The module unit is able to be attached to and removed from the first antenna.