PURPOSE: To obtain an uneven board having a surface pattern free from heat deterioration or loss of strength, by pressing the bend part of a synthetic resin board having uneven bend part, extruded from a mold, between an embossing roll and a smooth roll, and by recovering the bend part to an uneven form.

CONSTITUTION: The synthetic resin board material 2 having the uneven bend part 1 is extruded from the mold 3. The uncured material 2 is pressed between the embossing roll 4 having an uneven pattern and the smooth roll 5 at a temperature of 100W150°C under a pressure of 5W50 kg/cm2, and patterned while being flattened resisting the self elasticity, then recorved to the original unenen shape by sucking the interior of the board material 2 with the sizing die 6