A new high-pressure polymorph of NaBiO3 (hereafter beta-NaBiO3) was synthesized under the conditions of 6 GPa and 600 degrees C. The powder X-ray diffraction pattern of this new phase was indexed with a hexagonal cell of a = 9.968(1) angstrom and c = 3.2933(4) angstrom. Crystal structure refinement using synchrotron powder X-ray diffraction data led to R-WP = 8.53% and R-P = 5.55%, and the crystal structure was closely related with that of Ba2SrY6O12. No photocatalytic activity for phenol decomposition was observed under visible-light irradiation in spite of a good performance for its mother compound, NaBiO3. The optical band-gap energy of beta-NaBiO3 was narrower than that of NaBiO3, which was confirmed with density of states curves simulated by first-principles density functional theory calculation.