To provide a
phosphoric acid-based glass having a low heat expansion coefficient.SOLUTION: An
optical glass has, on a
mass basis, a content of B2O3 of 3.00% or more and 70.00% or less, a content of P2O5 of 47.00% or more and 80.00% or less, a content of Al2O3 of 13.00% or less, a content of Li2O of 0.01% or more, a content of Na2O of 5.00% or less, a content of CaO of 18.00% or less, a content of ZnO of 23.00% or less, a total content of (P2O5+B2O3+SiO2) of 66.00% or more and 84.00% or less, a total content of (MgO+CaO+SrO+BaO) of 26.00% or less, provided that a total content of (P2O5+B2O3+SiO2) of 69.00% or more and 84.00% or less when a total content of (MgO+CaO+SrO+BaO) is 15.00% or more and 26.00% or less, a total content of (Li2O+Na2O+K2O) of 15.00% or less, a
mass ratio of (P2O5 / B2O3) of 18.00 or less, a
mass ratio of (Na2O / (Li2O+Na2O+K2O)) of 0.50 or less, a total content of (MgO+CaO) of 2.00% or more, a
mass ratio of ((Li2O+BaO) / B2O3) of 0.59 or less, a
mass ratio of ((Al2O3+BaO) / Li2O) of 2.77 or less, a
mass ratio of ((MgO+CaO) / (Li2O+Na2O+K2O)) of 6.10 or less, a mass ratio of ((MgO+CaO+SrO+BaO+ZnO) / (P2O5+B2O3+SiO2)) of 0.36 or less, a
refractive index nd of 1.70000 or less, an
Abbe number νd of 60.00 or more, and an average
linear expansion coefficient α at 100°C-300°C of 130×10-7 / K or less.SELECTED DRAWING: None