Yoon plunged the country into political chaos with his December 3 bid to suspend civilian rule, a move which lasted just six hours before lawmakers defied armed soldiers in parliament to vote it down.
He could face life in jail or the death penalty if convicted, although South Korea has not executed anyone in decades.
Separate from criminal judicial proceedings, the Constitutional Court is now deliberating whether to formally dismiss Yoon as president or reinstate him.
South Korean President Yoon Suk Yeol, who has been impeached and is now in detention, was indicted on charges relating to his attempt to declare martial law.