Authorities believe the man, who is in his 50s, began the fire in southeast Uiseong County when he performed an ancestral rite at a family grave on March 22, an official from Gyeongbuk Provincial Police said on Sunday.
"We are in the process of verifying evidence," the official said.
In South Korea's legal system, booking involves registering a suspect but might not coincide immediately with arrest or charges.
Yonhap news agency said the man had denied the allegations.
The fire burned about 48,000 hectares, destroyed an estimated 4000 structures, and forced tens of thousands of people to evacuate.
By Friday, the blaze was largely contained, although firefighters were still battling small hotspots that had sprung up on Saturday.
The Uiseong fire and other blazes across the country last week killed at least 30 people and sparked calls for national reforms to tackle such disasters, which experts say are being exacerbated by climate change.
The forest service said on Sunday another wildfire broke out in a southern area near Suncheonsi, and authorities had deployed 23 fire trucks, four helicopters and 123 firefighters.
