To provide a continuous method for producing a lightweight honeycomb with good strength, heat resistance, and durability, an apparatus for the continuous production of the honeycombs, a honeycomb with novel constitution, and a method for the continuous production of a plate material (plywood) using the honeycomb as a core material.

A pattern in which notch parts 21 penetrating a plate from the surface to the back and non-notch parts 22 are arranged alternately on the same line of a plate surface. Another pattern whose phases of the notch parts 21 and the non-notch parts 22 are dislocated from those of the pattern is formed in parallel with the pattern, and a mesh plate equipped with a mesh in which hexagonal holes 23A are adjoining each other is formed by expanding each notch part 21. Next, a honeycomb is obtained through a process in which sidewall parts 22C for partitioning each hole 23A is corrected to be perpendicular to the surface of the mesh plate.