To provide a continuous caster and casting method for a large cross section cast piece, free from casting defects and superior in inner quality.

A tundish 2, a mold 3, a carriage 4 to draw and guide a molten steel vertically downwards from the mold 3, the first electrode 11 closely above the molten steel surface in the tundish 2, the second electrode 12 closely above the molten steel surface in the mold 3, the third electrode 4 which also served by the carriage 4, a power source 15, and a conduction control device to exchange power supply between the primary conducting state which connects power source 15 to both the first electrode 11 and the second electrode 12, and the secondary conducting state which connects power supply to both the second electrode 12 and the third electrode 4, are equipped. Molten steel both in the tundish 2 and in the mold 3 is plasma heated while molten steel is being poured from the tundish 2 to the mold 3, and the top end of the cast piece drawn out from the mold 3 is plasma-heated after the completion of pouring from the tundish 2.