WASHINGTON — Joseph R. Biden III, the former attorney general of Delaware and the elder son of Vice President Joseph R. Biden Jr., died on Saturday in Bethesda, Md. He was 46.

The cause was brain cancer, his father said.

Mr. Biden had spent more than a week receiving treatment at the Walter Reed National Military Medical Center, where he died.

In a statement Saturday night, the vice president said, “It is with broken hearts that Hallie, Hunter, Ashley, Jill and I announce the passing of our husband, brother and son, Beau, after he battled brain cancer with the same integrity, courage and strength he demonstrated every day of his life.”

The statement went on to say, “In the words of the Biden family: Beau Biden was, quite simply, the finest man any of us have ever known.”