Source: http://news.bbc.co.uk/2/hi/americas/7035294.stm
Christian Von Wernich, 69, was convicted for involvement in seven murders, 42 abductions and 31 cases of torture during the 1976-83 "Dirty War".
Survivors say he passed information he obtained from prisoners to the police.
As he was sentenced, Father Von Wernich showed no emotion. Protesters torched his effigy outside the court.
The trial in the town of La Plata, 60km (35 miles) south of Buenos Aires, had lasted for three months.
Father Von Wernich initially avoided prosecution by moving to Chile, where he worked as a priest under a false name.
However, he was eventually tracked down by investigators and extradited to Argentina in 2003 when amnesty laws passed at the end of military rule were declared unconstitutional.
Participant
At the trial, several former prisoners said the former Roman Catholic priest used his office to win their trust before passing information to police torturers and killers in secret detention centres.
They say he attended several torture sessions and absolved the police of blame, telling them they were doing God's work.
"Von Wernich participated assiduously and maintained direct contacts with the detainees," the prosecution said in its indictment.
Father Von Wernich's lawyers said the case against him had more doubts than certainties and that he had been obliged to visit police detention centres as part of his duties.
The priest said he had never violated the prohibition against revealing information obtained in the sacrament of confession and accused those torture victims who gave evidence in court of being influenced by the devil.
"False testimony is of the devil, because he is responsible for malice and is the father of evil and lies," he said.
Outrage
Once the judge announced the sentence, observers inside the courthouse erupted with relief and jubilation. Outside, crowds cheered and set off fireworks.
"It's a historic day, a wonderful day... it's something we mothers didn't think we'd live to see," said Tati Almeyda, a member of the Mothers of the Plaza de Mayo, a group of women seeking their sons and daughters who disappeared under military rule.
"Justice has been done. The Catholic Church was an accomplice," she told the Reuters news agency.
The BBC's Daniel Schweimler in Buenos Aires says Father Von Wernich's actions caused particular outrage in Argentina because he had abused the trust that believers placed in him.
While human rights activists and survivors will be celebrating the verdict, they will now shift their attention to the Roman Catholic Church in Argentina, our correspondent says.
The Church remained silent on the case ahead of the verdict, but it will again face questions about the role it played during military rule, he adds.
Between 10,000 and 30,000 people were killed or disappeared before Argentina returned to civilian rule with the election of President Raul Alfonsin in October 1983.