PURPOSE: To pattern the surface of a corrugated board, then improve its decorative effects and provide the board with functional effects such as weather- proofness in a continuous manner, without the use of any special equipment.

CONSTITUTION: A thermal transfer film 7 having a pattern or functional effect transfer layer, and a synthetic resin molded board 4 extruded from an extrusion die 3 by an extrusion machine 2 are supplied to an area between corrugation rolls 5, 6, and the synthetic resin molded board 4 is corrugated using said rolls 5, 6. At the same time, the pattern and functional effect transfer layer of the thermal transfer film 7 is thermally transferred to the surface of the synthetic resin molded board.