This paper describes a largely deformable surface type neural electrode array based on polydimethylsiloxane (PDMS) for cortical use. Noncracked and reliable metal patterns were fabricated successfully on PDMS substrate by employing an intermediate parylene layer. The mechanical and electrical stability of the fabricated electrode arrays was demonstrated by repeatable bending test using a custom-designed bending test module. Also the adhesion of the electrode structure consisting of PDMS, parylene and metal layers was proven by ASTM tape test. The electrode impedance was measured in phosphate buffered saline (PBS) solution at 37°C over three months and analyzed using equivalent circuit models. Based on these results, it is concluded that the suggested electrode array provides a largely deformable structure with mechanical integrity and electrical stability, which can withstand mechanical stresses when inserted through a small trephination hole in the skull and expanded in the small room between the cortex and the skull without damage to the electrode array.