North Wales Police was called to Maes Padarn in Llanberis at 03:00 GMT on Sunday by the ambulance service.
The man was taken to hospital where he later died.
Police said a man from the area had been arrested and the death was being treated as suspicious, pending the results of a post mortem examination.
A forensic team is due to start examining the crime scene on Sunday afternoon as part of the investigation.
Officers are not looking for anyone else in relation to the death.
A man has been arrested following the death of a 70-year-old in Gwynedd.