Shin Ok-ju, who founded the Grace Road Church, convinced 400 people to move to Fiji in 2014, claiming they would be safe from imminent natural disaster
Once there, their passports were taken away and many of them reported being beaten to "drive out evil spirits", reported the BBC.
Shin was arrested last July.
On Monday, a South Korean court found Shin guilty on several criminal charges including violence, child abuse and fraud.
"The victims suffered helplessly from collective beatings and experienced not only physical torture but also severe fear and considerable mental shock," said a sub-court of the Suwon District Court.
"Heavy punishment is inevitable against illegal acts carried out in the name of religion," it said.
Five other church officials were also sentenced. There has been no comment from the church.
Grace Road Church has been described as heretical by mainstream South Korean Christian groups.
Shin preached that a global famine was imminent but that she and her followers would be safe in Fiji.
The church had leased land near the capital, Suva, and built a large business empire, with labour provided by Shin's followers.
It won several construction contracts from the Fijian government and a business excellence award from the prime minister.
Reports say several million people in South Korea belong to groups that promote fringe beliefs and interest in these groups is growing.
( With inputs from IANS )