To provide a plastic foam board improved in surface hardness and restrained in the generation of whitening phenomenon.

Of a cap sheet 2, a back sheet 3 and a liner sheet 4 that constitute a foam board 1 of a hollow structure, the back sheet 3 and the liner sheet 4, which have a surface functioning as an outside surface part showing itself to the outside of the foam board 1, are in the form of a three-layer sheet, and the outmost layers 32, 42 of these back sheet 3 and liner sheet 4 are composed of a mixture of polycarbonate and polyester.