Jo Min-ki had been accused of molesting at least eight people amid a string of #MeToo allegations in the country.
The actor was found dead at his home in Seoul, according to news agency Yonhap and the Korea Times, who cited police.
Min-Ki's roles were mainly in TV shows, but he also appeared in a number of films. He was due to be questioned by police next week, the reports said.
More about: #MeToo