Focusing device and method for adjusting laser focal length

The invention discloses a focusing device for adjusting the laser focal length. The focusing device comprises an automatic assembly line, a base, a laser measuring mechanism, a sample position switching mechanism and a laser generating and focal length adjusting mechanism. The base is located on one side of the automatic assembly line, and the laser measuring mechanism, the sample position switching mechanism and the laser generating and focal length adjusting mechanism are sequentially arranged on the base. The laser generating and focal length adjusting mechanism comprises a Z-axis support, an X-axis telescopic rod and a laser lens. One end of the X-axis telescopic rod is movably connected with the Z-axis support, and the laser lens is located at the other end of the X-axis telescopic rod and located above the automatic assembly line. The invention further discloses a focusing method. Sample cutting is carried out by moving the focal length multiple times, and the precision of focal length adjustment is imp