The invention discloses a laser shock strengthening method and device. According to the laser shock strengthening method, according to the relationship of machining strength and the thickness of an absorbing layer, machining strength of all areas to be machined of workpieces to be machined is substituted into the relationship of the machining strength and the thickness of the absorbing layer, thethicknesses of absorbing layers corresponding to the areas to be machined are obtained, under the same preset energy density and the pulse width, through changing the thicknesses of the absorbing layers of all the areas to be machined of the workpieces to be machined, and different machining strength can be obtained; through changing of the thicknesses of the absorbing layers, operation is easy, pulse laser parameters of a laser impact device do not need to be changed, and the technical problem that when area unequal-strength laser impact strengthening is carried out on parts in complex shapescurrently, pulse laser parameters of different areas need to be adjusted, programming is complex, and practicability of laser impact strengthening and operation efficiency are low is solved.