More than 330 people were killed in the attack, most of them children.
In May, Nurpashi Kulayev was convicted by a court in southern Russia.
The Supreme Court on December 26 upheld that verdict, rejecting appeals from his lawyers and relatives of the victims.
The head of a group of victims' relatives called Voice of Beslan, Ella Kesayeva, said on Ekho Moskvy that Kulayev's trial failed properly to investigate the circumstances of the raid and rescue efforts.
Survivors and victims' relatives have accused the Russian leadership of covering up for what they call a botched rescue effort by security forces.
A parliamentary committee report released on December 22 justified actions by security forces in the attack.
Investigating The Beslan Tragedy
WILL THE TRUTH BE KNOWN? As the second anniversary of the Beslan tragedy neared, Duma Deputy Yury Savelyev, a member of the official investigating committee, issued a 700-page report that veers sharply from the official explanation...(more)