Provided is an optical glass which can satisfy all of the following requirements: (1) it contains no environmentally undesirable components; (2) it can easily achieve a low glass transition point; (3) it has a high refractive index and high dispersion; (4) it can easily provide a glass having a superior visible light transmittance; and (5) it has superior resistance to devitrification during preparation of a preform. The optical glass has a refractive index nd of 2.0 or more, an Abbe's number νd of 20 or less, a glass transition point of 450° C. or below, and a glass composition, in % by mass, of 70 to 90% Bi2O2, 4 to 29.9% B2O2, 0.1 to 10% Li2O+Na2O+K2O, and 0 to 2.5% SiO2+Al2O2 and is substantially free of lead component, arsenic component, F component, TeO2, and GeO2.