The invention relates to a method of amplifying a laser beam which includes steps consisting in performing an optical pumping of an amplifying crystal so as to inject into the crystal an optical pumping energy E.sub.total, amplifying the laser beam by means of the amplifying crystal and an optical system with N passes, that is, designed to inject the laser beam into the amplifying crystal N times, N being an integer>1. The optical pumping is temporally divided into n partial pumpings, the optical energy of a partial pumping being a fraction of E.sub.total, n being an integer 2.ltoreq.n.ltoreq.N and in that the laser beam is injected into the amplifying crystal at least once after each partial pumping.