PURPOSE: To prevent the accumulation of water in a plate-like foaming synthetic resin layer and to suppress the deterioration of adiabatic performance by forming a space in a boundary surface between a plate-like protective layer and the plate-like foaming synthetic resin layer in a composite adiabatic board into which both layers are integrated.

CONSTITUTION: The upper layer and the lower layer are adhered by providing projections to the bottom of the upper layer of a plate-like protective layer 2, or providing projections on the top of the lower layer of a plate-like foaming synthetic resin layer 3 or lying a spacer between the upper layer of the plate- like protective layer 2 and the lower layer of the plate-like foaming synthetic resin layer 3. Accordingly, a space 4 is formed between the upper layer of the plate-like protective layer 2 and the lower layer of the plate-like foaming synthetic resin layer 3, and the air passes through the space 4, so that the water content going up to the plate-like foaming synthetic resin layer 3 can be better vaporized to the outdoor.