The unidentified 58-year-old taxi driver was found in an abandoned stone quarry on Sunday in Mungyong wearing only his underwear.
Police found the man with a wound on the side of his torso and nylon strings tied around his neck, arms and stomach.
Officers believe the man, whose surname is Kim, killed himself without assistance by nailing his feet to the cross, tying his neck to it and stabbing himself in the side.
He is then thought to have drilled holes in his hands and slipped them over nails on the cross.
The site where he was found is around 115 miles south-east of Seoul.
Officials simulated some elements of the crucifixion and concluded that an adult male could perform the act on his own, according to Gyeongbuk Provincial Police Agency.
There were also allegedly two smaller crosses erected on each side of the cross he was nailed to, as well as a propped-up mirror nearby so the man could witness his own suffering.
Also found were nails, a hammer, an electric drill, pieces of wood and instructions on how to build crosses inside a tent near the scene.
Police speculated the man was a devout Christian and that his 'deep religious faith' may have helped him endure 'immense pain.'
An autopsy showed the man died of bleeding from the stab wound and suffocation, police said.
Popular representations of the death of Jesus Christ depict him crucified between the crosses of two thieves, wearing a crown of thorns, a white cloth over his loins, with a wound on his side from a Roman soldier's spear. Source