Abstract: Detecting unit comprises position-sensitive detector 1 and collimating system 2, situated in front of its window 19. Collimating system being made in the form of honeycomb structure comprising multitude of tubular channels for transmittance of diffracted X-ray radiation. Walls of adjacent tubular channels are fused together. Outlet ends of the channels, forming outlet end face 22 of the collimating system, are oriented towards window 19 of the position-sensitive detector. Outlets of the channels in outlet end face of the collimating system 2 are arranged in several rows along window 19 of the position-sensitive detector 1. Walls of the tubular channels are formed from material absorbing X-ray radiation. Collimating system 2 is installed with possibility of adjusting its position relative to the window 19 alignment of the position-sensitive detector. The embodiment specified provides for prevention of the difractograms distortion and the increase of sensitivity of the detecting unit.