A military court in Kabul ordered the soldier, Abdul Sabor, to be hanged. An appeal can be lodged.
It is not clear when the soldier was convicted of the crime.
The four French soldiers were killed on January 20 in Tagab district of Kapisa province. A month earlier, another Afghan soldier killed two members of the French Foreign Legion on December 29.
The casualties prompted France’s new president Francois Hollande to withdraw combat forces from Afghanistan earlier than planned. France will pull 2,000 French combat troops out of Afghanistan by the end of the year and leave around 1,400 soldiers behind to help with training and logistics.
The death of the French troops was one of the latest cases of attacks in which Afghan soldiers, or insurgents disguised in their uniforms, turn their weapons on coalition forces.
Such attacks have fuelled distrust between foreign troops and Afghan forces.
Last year there were a total of 21 such attacks, killing 35 coalition service members, according to Nato figures.