Object: to develop a method of reducing internal defects in continuous casting of thin cast pieces to improve a yield of manufacture.
Constitution: after casting a cast piece, of which central portions at the short sides after casting protrude 5 to 10 nm beyond end portions of the cast piece with cooling at short sides controlled, the cast pieces are rolled with a rolling reduction of 10 to 45 % of a thickness of the cast piece while a thickness of an unsolidified phase in the cast piece at the shorter sides amounts to 50 to 80% of a thickness of the cast piece.