Method and device for cutting machined target from two surfaces by using ultra-short pulse laser

The invention relates to a method and a device for cutting a machined target from two surfaces by using ultra-short pulse laser. The method comprises the following steps of providing a first laser beam and a second laser beam; focusing the first laser beam on the surface of a first side of the machined target so as to cut the surface of the first side; focusing the second laser beam on the surface of a second side, opposite to the first side, of the machined target so as to cut the surface of the second side; simultaneously moving focal points of the first laser beam and the second laser beam to the interior of the machined target, and forming a corresponding cutting area in the machined target; and when the cutting areas of the first laser beam and the second laser beam formed in the machined target are intersected, cutting the machined target apart. The invention also relates to the device for cutting the machined target by using the method.