The invention aims to provide optical glass which has high refractivity, low chromatic dispersion and relatively high stability, a prefabricated member manufactured by the optical glass, and an optical element. The optical glass comprises the following components by mass relative to total mass of oxides: 8.0-40.0% of B2O3, 15.0-80.0% of Ln2O3, wherein Ln is more than one selected from a set which is composed of La, Gd, Y and Yb. Relative to the mass of the oxides except for an F component, the optical glass comprises 5.0-50.0% of the F component by mass. Furthermore the optical glass has refractivity (nd) in 1.20-1.80, and an Abbe number (nud) in 45-65.