To provide a core material for a building material for conserving forests and achieving inexpensive and sustainable supply by using a processed material of albizzia falcataria, which is strong and hard to break, and capable of securely holding nails or screws by using an adhesive.

The albizzia falcataria, a planted tree of a pea family, which grows to a mature tree in five or six years, is used for core material for a building material. Dried albizzia falcataria wood is not used as it is, but used as a processed material such as a plywood, a veneer board or a laminated lumber, or a block material formed by laminating the laminated lumber with a plywood, a particle board, a fiber board or the like.