An optical glass that substantially does not contain any Ta2O5 and has high-refractivity low-dispersion optical properties and various optical parts made of such optical glass are provided stably at a low cost, and an optical part made thereof is provided, the optical glass having a glass composition comprising, by weight %, 0 to 7% of SiO2, 18 to 30% of B2O3, provided that the total content of SiO2 and B2O3 is 23 to 35%, 2 to 10% of ZnO, 30 to 50% of La2O3, 0 to 20% of Gd2O3, 0 to 20% of Y2O3, provided that the total content of La2O3, Gd2O3 and Y2O3 is 45 to 60%, 3 to 8% of ZrO2 and 3 to 12% of Nb2O5, the total content of these components being at least 95% by weight, the optical glass having a refractive index [nd] and an Abbe's number [&ngr;d] which satisfy specified relational expressions.