Evaluation of the residual stress state in a surface, obtained by means of the ball-end milling process, is important to ensure the reliability of the machined product during its life cycle. X-ray diffraction is one of the techniques most commonly used for evaluating residual stresses. A review of the specialised bibliography shows the shortage of a methodology for this type of studies on materials with more than one crystalline phase. In this experimental research for evaluating the state of residual stress in a series of samples machined with a ball-end mill on the Ti-6Al-4V ELI titanium alloy, it was found that they were subject to compressive residual stress. An electropolished surface of the same material was taken as a reference pattern. The X-ray diffraction analyses were carried out on the crystallographic planes {1012} and {1013} of the alpha phase of the alloy.