Abdelkarim al-Kafarna said Friday he found a tomb consisting of nine burial holes with bones and some clay pots.
Archeologists in Gaza believe the site is about 2,000-year-old, dating back to the Roman era, when the territory was part of the far-flung Roman Empire. But they say further tests are needed to determine the exact age.
Al-Kafaran said he found it by accident after heavy rains this week unearthed parts of the underground chamber.
Gaza, now ruled by the Islamic militant group Hamas, is on the route between Egypt and ancient Levantine civilizations. It is packed with ancient archaeology endangered by urban sprawl, conflict and years of neglect.