PURPOSE: To easily produce a honeycomb structural material in a low cost and to easily handle it in a time of storing and transporting, etc.

CONSTITUTION: A honeycomb structural material 40 is formed by mutually face to face matching hollow structural materials 10 of hexagon column shaped single body being separated and divided physically and connecting them. These plural numbers of hollow structural materials 10 are connected mutually with clips 46 being attached fitting in freely attachably and detachably extending over the peak parts 42. These hollow structural material 10 of hexagon column shape are formed with the hollow hexagon column body 10A being composed of two dividing half parts 14A, 14B. These two dividing half parts 14A, 14B are formed by bending a metal sheet, etc., with a press, etc., and each has four connecting walls among six walls 12A to 12F. These two dividing half parts are joined in freely attachably and detachably.