An experimental identification method of impact force acting on composite structures is presented. The experimental relation between force histories and strain responses is first determined through impact tests with an impulse hammer. By employing this relation, the location and history of impact force is identified using measured strains. The validity of the present identification method has been verified through the impact test of cantilevered CFRP stiffened panel. The method can also be applied to the impact force identification in CFRP laminated plates involving impact damages under a drop-weight impact test.