This paper focussed on the optimal machining parameters of Ball end milling process on AISI 4340 steel plates. Surface roughness will play an important role in quality aspect of manufacturing environment. Influencing of machining parameters such as spindle speed, Angle and depth of cut of ball end milling process is investigated. Mainly surface roughness of AISI 4340 steel plates during end milling process which investigated by employing Taguchi design of experiment and Analysis of variance (ANOVA). The significant parameters are identified by Signal to Noise ratio. The results of experiments represent Angle of machining is an influencing parameter in Ball end milling process.