Lam Wing-kee was detained for eight months after being abducted along with Gui Minhai in 2015. He was allowed to return to Hong Kong and then fled to Taiwan, where he reopened his bookstore.
On Facebook, Taiwanese President Lai Ching-te expressed regret over the publisher's death, according to Taiwan's CNA news agency.
"But the courage he leaves behind will not die out," the president wrote.
The Taiwanese news agency did not give a cause of death, but said he had suffered a relapse of cancer last year. Lam Wing-kee died on Thursday.
Gui Minhai was first arrested in October 2015 and sentenced in 2020 to ten years in prison, accused of “providing intelligence to a foreign power.”
