Optimal conditions for milling carbon/epoxy composite material were established by response surface methodology. The combination of cutting parameters such as cutting speed (Vc) and chip thickness (h) was set at various design points of a central composite design. Significant regression models describing the changes of vibration level, delamination of composite, cutting force, workpiece temperature were developed with the coefficient of determination greater than 0.90. Results suggested that beyond a threshold of vibration, the occurrence of delamination is regular. Vibration criterion was defined from the observations of the workpiece according to the delamination defect. The optimum milling conditions were graphically represented using design contour plots. The best combination of process variables was found, according to the cutting conditions. This new technique should help the operator to select the optimum cutting conditions such as cutting speed and feed rate (chip thickness) in order to avoid damage to the carbon/epoxy composite material T800S/M21 and increase machining productivity.