The impact bending behaviors of beam with open-cross section were investigated. The cantilever bending and three-point bending experiments were performed by a falling weight for aluminum specimens. The plastic deformation in the case of cantilever bending was larger than that of three-point bending. But, the elastic dynamic bending strain measured in the case of cantilever bending was smaller than that of three-point bending when the peak of the first strain pulse in the strain history is compared with each other. Thus, these behaviors are very complicated and quite different from the static one. That is, the elastic bending strain of the first strain pulse is reduced by the interference between the leading waves and the following reflected waves with the reversed phase which are reflected at the free end. These impact bending behaviors in the case of open-cross section beam are similar to those of the hollow section beam.