An optical glass has optical constants of a refractive index (nd) within a range from 1.73 to less than 1.80 and an Abbe number (νd) within a range from 43 to 55, comprises SiO2, B2O3, Y2O3, La2O3, ZnO and Li2O as essential components, is substantially free of lead component, arsenic component and fluorine component, has a ratio of SiO2/B2O3 of 0.30 to 1.55 and a ratio of Y2O3/La2O3 of 0.15 to 1.00, and has a glass transition temperature (Tg) of 620° C. or below.