In this study, the effect of cutting speed, feed rate, and depth of cut on surface roughness was experimentally examined in the processing of AISI 409 (ferritic chromium stainless steel) material. As cutting parameters, three cutting speeds (200, 300, and 400 m/min), three feed rates (0.1, 0.2, and 0.3 mm/rev), and three depths of cut (1, 2 and 3 mm) were selected. Turning tests in CNC machine were made according to Taguchi L27 orthogonal array and the signal/noise (S/N) ratios were used in the evaluation of the experimental results. By using Taguchi method, cutting parameters giving the optimum surface roughness (Ra and Rz) values were determined. The effect of control factors on the results was found with the help of Analysis of Variance (ANOVA). According to ANOVA results, the most important parameters affecting the surface roughness were determined as feed rate, depth of cut, and cutting speed, respectively. By conducting validation tests, the optimization was observed to be applied successfully.