An reader/writer performing a two-way communication with a contactless tag through electromagnetic induction and supplying electric power to the contactless tag, includes: an antenna circuit having an antenna coil for electromagnetically coupling with an antenna coil in the contactless tag, the antenna circuit provided in the plural number, a first amplifier circuit amplifying a signal which the antenna circuits send outside, a first switch provided between the first amplifier circuit and each antenna circuit, the first switch provided in the plural number, a second amplifier circuit amplifying a signal which the antenna circuit received, a second switch provided between the second amplifier circuit and each antenna circuit, the second switch provided in the plural number and a control circuit turning on a predetermined switch among the first switches and a predetermined switch among the second switches, wherein the antenna coil has a loop shape and a plurality of the antenna coils are provided adjacently each other in the same plane, and the loop of the antenna coil has a shape such that an adjoining region of the antenna coils becomes as small as possible.