An objective of the present invention is to provide a two-dimensional photonic crystal in which a complete photonic band gap (PBG), i.e. a photonic band gap that is effective for both a TE-polarized light and a TM-polarized light within a predetermined wavelength range, is created and an adequate width of the complete PBG can be ensured. A slab-shaped body 21 consisting of a birefringent material is provided with holes 22 periodically arranged in a triangular lattice pattern, where a plane shape of the hole is an equilateral triangle. The PBG for the TE-polarized light and the PBG for the TM-polarized light can be independently set by adjusting anisotropy in the refractive index of the body 21, i.e. a refractive index in a direction vertical to the body 21 and a refractive index in a direction parallel to the body 21. This construction makes it possible to ensure an adequate width of the complete PBG.