The B4391 was closed while police, underwater search teams and mountain rescuers carried out the search.
North Wales Police say the man is believed to be Nicholas Davies, who has been missing from Llan Ffestiniog.
The death is not being treated as suspicious and the coroner for north west Wales will be informed.
The B4391 has been closed in both directions between Llan Ffestiniog and the B4407 junction for Ysbyty Ifan since about 17:00 GMT on Monday.
Det Ch Insp Brian Kearney at Caernarfon CID said: "The man was pronounced dead at the scene and although he's yet to be formally identified we believe it's missing Llan Ffestiniog man Nicholas Davies.
"Mr Davies' family have been informed. Our thoughts are with them at this difficult time."
A man's body has been found following an extensive search on the outskirts of Blaenau Ffestiniog in Gwynedd, police have confirmed.