Influences of electron beam (EB) irradiation on magnetostriction and its susceptibility of Fe 2.6 Sm alloy thin films have been investigated. The alloy thin film deposited on a (100) plane of a silicon wafer is prepared by using a direct current magnetron sputtering apparatus. The irradiation enhances compressive magnetostriction and its susceptibility. The large magnetostriction of the irradiated Fe 2.6 Sm sample occurs, because the irradiation prevents generating the Fe 3 Sm crystalline with small magnetostriction. On the other hand, the high susceptibility is explained by randomization, induced by EB irradiation, of Fe 2.6 Sm amorphous sample, where the magnetic moment rotates easily.