This study used an experimental methodology to improve the input parameters and outputs of the electrical discharge manufacturing process for the purpose of improving the metal surface roughness (Ra) as a measure of the process performance during machining of DIN 1.2080 alloy steel. Tagushi method is utilized as design and optimization approach. Four input parameters are considered, which are electrode diameter (D), discharge current (Ip), pulse on time (Ton) and the operating factor (η). Signal to noise ratio is used as an analytical tool. Through the final results of the adopted optimization methodology, the optimum values of the inputs were obtained as follows: electrode diameter at level1 (15mm), discharge current at level1 (9A), pulse on time at level2 (1200µs) and duty factor at level2 (0.8), the value of the surface roughness decreases by 2.05 times at the optimized process parameters than the initial process parameters, whereas it is decreased from 6.30 µm to 3.07 µm. Taking into consideration the standard (smaller is better). The results of the main effect diagram indicated that the factors: electrode diameter, and discharge current were the most important parameters influencing the surface roughness, followed by pulse on time, and duty factor.