In order to improve the surface characteristics of polymethylmethacrylate(PMMA), oxide thin film coatings were applied using the sol-gel dip-coating technique. The Si(OC₂H_5)₄, tetraethyl-ortho-silicate(TEOS) was used as a starting material for SiO₂ coating. The hardness of the alkoxy-derived oxide-coated PMMA was increased from 190 MPa for non-coated PMMA with increasing film thickness. By optimizing the heating conditions and the hydrolysis conditions, a maximum apparent hardness obtained in the present study was achieved 310 MPa using the withdrawal velocity of 5㎝/min and heat treatment at 90℃ for 5 hours, which is about 1.6 times larger than that of uncoated PMMA.