The infiltration of a nematic liquid crystal into synthetic opal with a three-dimensional periodic structure has been studied. The transmission and reflection spectra of nematic liquid crystal infiltrated opals were measured. The wavelengths of the stop band and the reflection peak shift by the infiltration with a liquid crystal due to the higher refractive index than that of air. Moreover, the stop band and reflection peak are shifted by the change of the refractive index of the liquid crystal infiltrated into opal.