To provide a heat insulating material for a building, which achieves excellent heat insulating effect, enables resource recycling, and prevents occurring of condensation.

Flat members 2 each formed of a paperboard and corrugated members 3 each formed by sequentially bending the paperboard into ridges and valleys, are alternately superposed on each other to obtain a plurality of laminated layers, whereby a plurality of capillaries 4 extending in a predetermined direction are formed between the flat members 2. Then, an internal heat insulating member 1A which is interposed between pillar members 6 with the capillaries 4 being directed toward the pillar members 6, and attached to an internal plate 7 of the building, and an external heat insulating member 1B which is interposed between the pillar members 6 with the capillaries 4 being directed almost in parallel with the pillar members 6, and attached to an external plate 8 of the building, are obtained. The internal heat insulating member 1A improves the heat insulating efficiency by a plurality of independent hermetically-sealed air layers formed by the capillaries 4. The external heat insulating member 1B prevents condensation by virtue of gentle convection generated in venting layers defined by the capillaries 4 along the pillar members 6. In addition, these heat insulating members 1A and 1B are formed of the paperboards, and therefore they can be recycled as resources.