The invention provides high-refraction-index and low-dispersion optical glass which has refraction index (nd) of more than 1.75 and Abbe number (nu d) of more than 35, and the imaging characteristic of the optical glass is not susceptible to the temperature change of use environment. By using SiO2, B2O3 and La2O3 as essential components and adjusting the component ratio, the optical glass is obtained, and the optical glass has the characteristic that the product of average linear expansion coefficient alpha at (-30)-(+70) DEG C and photoelastic constant beta at wavelength of 546.1 nm is less than 130*10<-12> DEG C<-1>*nm*cm<-1>*Pa<-1>.