Recoil force exerted on the substrate during a nanosecond laser ablation of silicon is measured. The ablation sample is placed at the end of a 400 $mu extrm{m}$ thick and 13 mm long silicon cantilever. The vibration amplitude of the cantilever induced by the recoil force is measured in real time with a probe beam. By comparing the deflection amplitude of the cantilever with a theoretical model, the recoil momentum is estimated. For laser irradiance in the order of 10$^$11/ W/$ extrm{cm}^2$, the recoil pressure reached a value over 40${ imes}$10$^$9/ Pa.