Although most fatalities in tsunami-related disasters are conjectured to be a result of drowning, injury risk owing to collision with other floating debris or fixed buildings has not been studied sufficiently. In this study, the impact force corresponding to the collision of a concrete block and drifting test body in a tsunami wave was experimentally investigated. The experiments were conducted using the Large Hydro-Geo Flume in the Port and Airport Research Institute, Yokosuka, Japan. The flume has length, width, and depth of 184 m, 3.5 m, and 12 m, respectively, with a piston-type wave-generator. In the experiment, a soft polyvinyl chloride (PVC) dummy and a PVC pipe with lids filled with water were employed as test bodies. Two acceleration sensors were attached to the head and ankle of the KM, and one sensor of the same type was attached at the top of the PVC pipe to investigate the impact of collisions.