A laser shock and supersonic vibration extrusion co-strengthening device and method. The device comprises a laser assembly, a vibration assembly, a hydraulic assembly and a connecting assembly. The method strengthens a hole (7) formed in a metal sheet (5) simultaneously by laser shock strengthening and supersonic vibration extrusion strengthening; a mandrel (1) is in clearance fit with the hole to constrain the hole, so as to avoid distortion of the hole and a hole angle when the laser shock is performed on an outer surface of a workpiece and to improve the strengthening effect of a hole wall; when the laser shock is performed on the outer surface of the metal sheet, supersonic vibration is applied by the mandrel in the hole; and a three-dimensional pressure stress distribution nearby the hole wall at a certain depth is formed under an interaction produced by power ultrasound and laser shock waves having a certain frequency, amplitude and modality, so that an inner surface having higher anti-fatigue performance and being smoother is provided to the hole. Defects of a traditional strengthening process are overcome, and the problem in strengthening the hole separately through the laser shock or supersonic vibration extrusion is solved.