There is provided a cast strip manufacturing method including: supplying a molten steel stored in a tundish (18) to a molten steel pool portion (16) formed by a pair of rotating cooling rolls (11) and a pair of side dams via an immersion nozzle (20); and forming and growing a solidified shell on a circumferential surface of the cooling roll (11) to manufacture a cast strip (1), in which a Si additive is added to the molten steel in the tundish (18), a Si concentration of the molten steel is adjusted to be within a fixed range, and a temperature of the molten steel in the tundish (18) is controlled to be within a fixed range.