A collimator lens located in a light path from a laser light source to an optical information recording medium. The collimator lens is constituted by a cemented lens which is composed of a biconvex lens and a meniscus lens, and an aspheric plastic lens in the form of a transparent thin synthetic resin film which is laminated on a lens surface of the biconvex lens on the side of or facing toward an optical recording medium. When calculated on the basis of a composite focal length f=10 mm, the collimator lens has an epaxial chromatic aberration correction rate (a) and a numerical aperture NA in the ranges of (1) (a) <2.2 .mu.m/nm and (2) 0.4>NA.gtoreq.0.12, respectively.