There is provided an optical control device including a plurality of line-defect waveguides provided in a photonic crystal; each line-defect waveguide including a multiplicity of dielectric pillars with a finite height arranged at lattice points of a two-dimensional Bravais lattice. The optical control device comprises: a first line-defect waveguide; a second line-defect waveguide provided with the dielectric pillars having a thickness different from that of the dielectric pillars of the first line-defect waveguide; and a third line-defect waveguide arranged between the first and second line-defect waveguides and provided with the dielectric pillars whose thicknesses are gradually varied from those of the dielectric pillars of the first line-defect waveguide to those of the dielectric pillars of the second line-defect waveguide along a wave guiding direction.