We study impact phenomena of small clusters subjected to thermal fluctuations on the basis of molecular dynamics simulation. From our simulation for colliding two identical clusters, it is found that the restitution coefficient for the head-on collisions can exceed unity when the colliding speed is smaller than the thermal velocity of one ``atom'' of the cluster. The averaged behavior can be understood by quasi-static theory of impact phenomena. It is also confirmed that our result is governed by the fluctuation theorem. This work is the collaborative research with H. Hayakawa (YITP, Kyoto Univ.).