He was convicted of contesting crimes against humanity.
The former Front National chief was convicted of the same charge in 2012 after saying France's Nazi occupation had been "not particularly inhumane".
France has strict laws against Holocaust denial.
Mr Le Pen told a journalist his remarks "corresponded to my thought that the gas chambers were a detail of the history of war".
Asked if "millions of deaths" could be called "point of detail", Mr Le Pen said: "It is not a million deaths, it is the gas chambers. I'm talking about specific things. I have not talked about the number of dead. I spoke of a system. I said it was a detail of the history of warfare."
As well as remarks about the Holocaust, Mr Le Pen said in 2014 that the Ebola virus could solve Europe's "immigration problem".
He was expelled from the party he founded last year by his daughter Marine Le Pen, the current leader, over his extreme beliefs.
In 2015, Ms Le Pen was acquitted of inciting hatred after comparing French Muslims to the Nazis who occupied France during the war.
Former French far-right leader Jean-Marie Le Pen has been fined 30,000 euros (Â£24,000; $34,000) for calling the Nazi gas chambers a "detail" of World War Two.