A device for focusing a laser light beam includes an emission source of a laser light beam along an optical emission path, first focusing means of the laser light beam in a focusing point (F) located at a focusing distance (D), means for adjusting the position of the focusing point (F) relative to the device, and means for detecting the focusing distance (D) active in feedback on the adjustment means, wherein the detection means detects a parameter characteristic of the light beam leaving the first focusing means and representative of the focusing distance (D). The characteristic parameter is the wavefront radius of curvature of the light beam leaving the first focusing means.