PURPOSE: To preclude the possibility that deformation and peeling between a core material and a surface layer material occur.

CONSTITUTION: A deck material 6 is formed in a long-sized plate, and mainly composed of a core material 7 made of expanded polyvinyl chloride and a surface layer material 8 made of rigid polyvinyl chloride covering the surface of the core material 7 and being integrally molded with the core material 7. Wood meal is mixed into a raw material at the time of injection molding in the surface layer material 8, thus suppressing the linear expansion coefficient of the surface layer material 8 to approximately four or five. The expansion ratio of the core material 7 is set to approximately two and a half times, and the linear expansion coefficient of the core material 7 after expansion is set to approximately four or five. Accordingly, the linear expansion coefficient of the surface layer material 8 and the linear expansion coefficient of the core material 7 are equalized approximately.