Abstract: The immersion microscope objective lens system of the present invention provides a numerical aperture of 1.3, a magnification of 40.times., a planatic image field even in the wide field of view and appropriately compensates for all aberrations. The immersion microscope objective lens system of the present invention comprises a structure including a plurality of lens groups G1 through G8 arranged along a common optical axis wherein the first lens group G1 from the object side of the lens system includes a planoconvex lens and a meniscus lens cemented to the planoconvex lens with its convex surface facing toward the image side of the lens system and wherein the second lens group G2 includes two positive meniscus lenses having convex surfaces facing toward the object side of the lens system and wherein the following condition is fulfilled: that n2 is larger than 1.70 where n2 is the refractive index in relation to the "d" line of the meniscus lens of the first lens group G1 (.lambda.=587.6 nm).