We demonstrate the light transmission characteristics in a photonic crystal (PC) slab with liquid crystal (LC) as an anisotropic medium. In PC slabs, the guided resonance occurs for normal incidence of light. In this study, we first fabricated a SiN PC slab without LC and observed this resonance. Also, we added an ellipticity to holes of the PC slab and observed a polarization filtering effect arising from the structural birefringence. Then, we filled the holes with LC. By making a phase transition in the LC, the resonant wavelength was tuned by maximally 33 nm. This will be applicable to surface-normal-type devices which control the transmission and polarization characteristics of light.