Provided are a photonic-crystal plate that forms an optical waveguide and an optical device assembly using the same, and more particularly, a vertical-type photonic-crystal plate and an optical device assembly configured to be easily integrated with surface-emitting light source devices and surface-receiving light detector devices. The photonic-crystal plate includes a plurality of cylindrical through holes formed in a thickness direction and arranged in a periodic crystal lattice structure. The plate further includes: a main crystal lattice defect that forms a main optical waveguide for passing lights in a direction perpendicular to the photonic-crystal plate; and a sub-crystal lattice defect that forms a sub-optical waveguide for causing light in a specific wavelength band among the lights passing through the main optical waveguide to be optically coupled and passing the coupled light in the direction perpendicular to the photonic-crystal plate.