Fodil Tahar Aouidate, 32, first appeared in court on May 27 but a judge delayed his trial to allow for a medical examination.
"The medical report shows that there are no signs of torture on his body," the judge told the court.
Aouidate showed no reaction when the judge handed down his death sentence, according to an AFP journalist at the trial.
He was one of 11 French citizens and a Tunisian handed over to Iraqi authorities early this year by a US-backed force in Syria which expelled the group from its last bastion.
A Baghdad court had already handed capital punishments to seven of the French militants and the Tunisian over the past week and Aouidate will now join them on death row.
HRW condemns France 'outsourcing' of IS trials to Iraq
Interrogated for four months, Aouidate alleged he was beaten to "confess" to the charges levelled against him.
During his first hearing he showed marks on his back to the judge, who requested a medical examination and report.
Human Rights Watch on Friday accused Iraqi interrogators of "using a range of torture techniques" and condemned France's "outsourcing" of trials of IS suspects to "abusive justice systems".
France has long insisted its adult citizens captured in Iraq or Syria must face trial before local courts, while stressing its opposition to capital punishment.
Iraqi law provides for the death penalty for anyone joining a "terrorist group" -- even those who did not take up arms.
Aouidate first went to Syria in 2013 and returned in 2014 with 22 members of his family to join IS, according to the French judiciary.
Authorities also linked him to Belgium's Salafist movement including Abdelhamid Abaaoud, the presumed mastermind of the 2015 Paris attacks.
France convicted two of Aouidate's sisters for "financing terrorism" for sending 15,000 euros to relatives in Syria.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ