The effects of P2O5 substitution on the coordination structure of a Bi3+ in Bi2O3–B2O3 glasses were examined by applying 11B and 31P MAS-NMR spectroscopy. Observation of the wide optical bandgap after the substitution revealed a substantial difference in the solvation shell structure between the P2O5 substituted and the P2O5-free Bi2O3-containing glasses, i.e., the P2O5 substitution replaced by the B2O3 is effective for forming the solvation shell, which leads to weak ligand field around a Bi3+. We report the optical properties of the Bi2O3–P2O5–B2O3 glass providing a wide optical bandgap (³3.6 eV) and high refractive index (³2.0).