The wooden artifact, dating to the late second century, was excavated from ancient ruins known as the Daifuku Remains in Sakurai City in the western Japanese prefecture of Nara, the team announced.
The wooden piece in the shape of z human face, 9 inches long by about 3 inches wide, was discovered along with wooden armors and bronze products during the excavation work, researchers said.
"Since we can recognize an 'eye', a part of a 'mouth' and two small holes which are gouged out part of the wooden board, we think the wooden object was used as a mask by an influential group of residents around the area to arrange a religious or solemn ceremony to show performed actions with the item," Teruhiko Hashimoto, chief researcher at Sakurai City's cultural assets division, told China's official Xinhua news agency.
The mask was made decades earlier than other wooden masks that have been found in the city, he said.
"We will continue further investigations into which kind of people wore the mask in the ancient times," he said.