1. An optical glass having a glass composition comprising, by weight %, 0 to 7% of SiO 2, 18 to 30% of B 2 O 3, provided that the total content of SiO 2 and B 2 O 3 is 23 to 35%, 2 to 10% of ZnO, 30 to 50% of La 2 O 3, 0 to 20% of Gd 2 O 3, 0 to 20% of Y 2 O 3, provided that the total content of La 2 O 3, Gd 2 O 3 and Y 2 O 3 is 45 to 60%, 3 to 8% of ZrO 2 and 3 to 12% of Nb 2 O 5, the total content of these components being at least 95% by weight, the optical glass having a refractive index &lsqb;nd&rsqb; and an Abbe's number &lsqb;&ngr;d&rsqb; which satisfy all of the following relational expressions, 1.795&lE;nd&lE;1.850 41.0&lE;&ngr;d&lE;44.5 nd&gE;−0.01×&ngr;d&plus;2.24.