A composite right/left-handed line device includes plural electrodes, plural dielectric substances and plural magnetic substances. The plurality of electrodes each include a pair of electrode plates, and a connection piece connected to the pair of electrode plates. The plurality of electrodes are disposed at regular intervals in a thickness direction between a pair of input terminals and a pair of output terminals. The plurality of dielectric substances are interposed between opposite surfaces of the pairs of electrode plates of adjacent two of the electrodes. The plurality of magnetic substances are disposed adjacently to the dielectric substances, respectively. The plurality of magnetic substances are interposed between opposite surfaces of the connection pieces of adjacent two of the electrodes.