  We study evaporation process of black strings which are typical examples of
Kaluza-Klein black holes. Taking into account the backreaction of the Hawking
radiation, we deduce the evolution equation for the radion field. By solving
the evolution equation, we find that the shape of the internal space is necked
by the Hawking radiation and the amount of the deformation becomes large as the
evaporation proceeds. Based on this analysis, we speculate that the
Kaluza-Klein black holes would be excised from the Kaluza-Klein spacetime
before the onset of the Gregory-Laflamme instability and therefore before the
evaporation.
