The present invention provides a polymer substrate with a hardcoat layer exhibiting excellent environmental resistance and wear resistance. A polymer substrate (60) is 1-20 mm thick and a hardcoat layer (70, 80) on the surface thereof comprises: an underlayer cured layer (70) with a thickness of 1-20 μm, and including 10-90 parts by weight of a multifunctional acrylate, and 90-10 parts by weight of inorganic oxide fine particles and/or a silicon compound hydrolytic condensate; and a silicon oxide layer (80) which is in direct contract with the underlayer cured layer, is formed by PE-CVD with an organosilicon compound as the starter material, and satisfies all of the following conditions (a)-(c): (a) the film thickness of the silicon oxide layer is 3.5-9.0 μm; (b) the maximum indentation depth of the surface of the silicon oxide layer by nanoindentation measurement at a maximum load of 1 mN is 150 nm or less; and (c) the limit compression ratio K of the silicon oxide layer is at most 0.975 in a 3-point bending test of the polymer substrate with a hardcoat layer having been subjected to indentation deformation that causes the surface on which the silicon oxide layer is layered to be indented.