A waveguide structure including a plurality of unit structures, each of which at least includes a first conductive plane and a second conductive plane, which are arranged to partially face with each other, a plurality of transmission lines with one ends being open ends, which are disposed in a plane, positioned opposite to the second conductive plane, in a layer different from the first conductive plane and the second conductive plane, and at least one conductive via, which electrically connect between the first conductive plane and other ends of the transmission lines.