A first antenna section included in an antenna has a first conductor, supplies electric power to a plurality of tags, and transmits electromagnetic waves to and receives electromagnetic waves from the plurality of tags. One end of the first conductor is a feeding point and an other end of the first conductor is an open end. The first conductor is connected to a reader-writer device for communicating with the plurality of tags. The first conductor can output electromagnetic waves. A second antenna section included in the antenna has a second conductor one end of which is a feeding point, an other end of which is an open end, and which is opposite to the first conductor of the first antenna section with the plurality of tags therebetween.