In neural prosthetics, stimulation electrodes are one of the most important components for stimulating neural tissue. It is known that the surface roughening of stimulation electrodes can improve their performance. In this study, we describe a method of producing platinum electrodes with a porous surface by anisotropic etching. Anisotropic etching was achieved by applying a DC voltage to a platinum electrode in physiological saline. The charge injection capacity Qinj almost doubled after etching, compared with that before etching. Furthermore, continuous current pulsing to the porous electrode in phosphate-buffered physiological saline for four months did not show any apparent deterioration in surface morphology or electrochemical properties, suggesting that the proposed porosification method improves the performance of stimulation electrodes.