Quoting Wikipedia on Guillotine:
The guillotine remained the official method of execution in France until the death penalty was abolished in 1981. The last guillotining in France was that of torture-murderer Hamida Djandoubi on September 10, 1977.
What happened next? Have they been dismounted? This does not seem really plausible because of their importance in French history. I suppose a couple of them are in history museum, but what about the others?