A photonic crystal device according to the present invention includes: a first dielectric substrate 104 having a first lattice structure, of which the dielectric constant changes periodically within a first plane; a second dielectric substrate 105 having a second lattice structure, of which the dielectric constant changes periodically within a second plane; and an adjustment device (pivot 303) for changing a photonic band structure, defined by the first and second lattice structures, by varying relative arrangement of the first and second lattice structures. The first and second dielectric substrates 104 and 105 are stacked one upon the other.