The group, who was on a trip to do wood work from the province's Phuc Trach Commune, said the cave's entrance is covered by forest trees in the territory of Phong Nha-Ke Bang National Park.
The newly discovered cave is said to be 3km east of Thien Duong (Paradise) Cave and 300m above sea level.
According to initial accounts, the new cave is said to be on the same grand scale as Paradise, is very long and has an inner stream.
The discovery comes as Quang Binh has been catapulted onto world travel lists as one of the most coveted destinations for cave explorers.
The province has four caves with tours running daily,Son Doong, Tu Lan, Paradise and Phong Nha.
Son Doong, which was discovered in 2009, is said to be the world's largest cave, according to the British Cave Research Association.
Nguyen Chau A, who works closely with British cave explorers to run sustainable tours through Son Doong and the Tu Lan caves, said there are still more caves in the area that have not yet been discovered.
In a recent trip to Tu Lan Cave, a British caver told Viet Nam News that she believed there are a lot of caves around the site.
Local authorities expect cave-related tourism to bolster the local economy and reduce illegal forest logging.
