According to one embodiment, a reading apparatus for reading a wireless tag includes a housing having a chamber and an opening providing an entrance to the chamber, a door attached to the housing and covering the opening when closed and permitting access to the chamber when opened, and an antenna within the housing and configured to emit a radio wave to read information from a wireless tag inside the chamber, a radiation surface of the antenna being parallel to a first inner wall surface and a second inner wall surface of the housing facing each other. The distance between the first and second inner wall surfaces is at least one half of a wavelength of a radio wave emitted from the antenna, and is a length based on an odd number multiple of a quarter of the wavelength.