A glass composition that simultaneously has a low temperature coefficient of refractive index and a good light transmittance, being suitable for use in environments of intense temperature change. There is provided an optical glass containing SiO2, B2O3 and La2O3, which has a temperature coefficient (20° to 40° C.) of relative refractive index (546.07 nm) of 10.0×10−6 (° C.−1) or below. Further, there is provided an optical glass mentioned above having a temperature coefficient (20° to 40° C.) of relative refractive index (546.07 nm) of 4.6×10−6 (° C.−1) or below. Still further, there is provided an optical glass mentioned above having an internal transmittance (τ;10 mm) at 400 nm of 80% or higher.