According to Korea Joongang Daily, the 21-year-old victim, with the surname Lee, died at 2.20pm local time Saturday from the injuries he received while cleaning cables in a freight elevator at the construction site.
"The labour union said the worker slipped and fell into a gap between an elevator and the edge of a partially built hallway, and his head and chest got stuck," the newspaper reported.
"He was immediately sent to a hospital, where he died."
Ordered by Italian oil major Eni, the FPSO is destined for the Goliath field in Norway's Barents Sea and will be able to store about 1 million tonnes of crude oil.
Production is expected from mid-2015. Investigations into the recent fatality are underway with the last worker dying at the Hyundai Heavy Industries shipyard in November.
HHI workers also recently knocked back a pay rise with reports suggesting they are also dissatisfied with safety conditions.
They last took industrial action in November.