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Bignone, 85, had already been sentenced to 25 years in prison for "illegal privation of liberty and torture of the political prisoners."
He became president of Argentina in 1982 after the country's humiliating defeat in the Falklands War and turned over power the following year to democratically-elected president Raul Alfonsin.
Since amnesty laws were repealed in 2005, Argentine courts have convicted more than 200 leaders of the military regime, and cases have been opened against 800 former military and police officials.
Human rights groups estimate that as many as 30,000 people were killed or went missing during the military regime, which waged a "dirty war" against the left.