To provide an objective lens used for an optical information recording/reproducing device capable of recording/reproducing information with high accuracy to/from different types of optical discs and forming a satisfactory spot on a recording surface by suppressing aberration.

The objective lens is a cemented lens including two optical elements made of different materials and cemented via a cementing surface. When refractive indices of first and second optical elements to a beam having a first wavelength are defined as nB1 and nB2, respectively, refractive indices of the first and the second optical elements to a beam having a second wavelength are defined as nR1 and nR2, respectively, a radius of curvature, a conical coefficient and a 4th non-spherical face coefficient of the cementing surface are defined as r2, k2 and A42, respectively, and a focal distance of the objective lens when the beam having the first wavelength is used is defined as f1, conditional expression (1) is satisfied.