A cell that configures an electromagnetic band-gap structure, comprises a first flat conductor and a second flat conductor arranged opposing each other, a first coupling conductor that is positioned between the first flat conductor and the second flat conductor, is that electrically connected to the first flat conductor, and that has an end that is not connected to the second flat conductor, a second coupling conductor electrically connected to the first flat conductor and the second flat conductor, and a first conductor strip electrically connected to an end of the first coupling conductor and the second coupling conductor.