The body was found in the Lorengau General Hospital earlier on Monday, Manus Island Police Commander David Yapu told the BBC.
The Tamil man, 32, died in a suspected suicide after receiving treatment for mental illness, refugee advocates said.
Australia controversially holds refugees and asylum seekers who arrive by boat in centres on Manus Island and the Pacific nation of Nauru.
Nine detainees have died since 2013 - including six at the Manus centre, which is due to close on October 31.
Last month, the US accepted the first of up to 1,250 refugees under a resettlement deal.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
About VDC
Doraiah Chowdary Vundavally is a Software engineer at VTech . He is the news editor of SocialNews.XYZ and Freelance writer-contributes Telugu and English Columns on Films, Politics, and Gossips. He is the primary contributor for South Cinema Section of SocialNews.XYZ. His mission is to help to develop SocialNews.XYZ into a News website that has no bias or judgement towards any.