PURPOSE: To easily obtain a three-dimensional honeycomb structure in a state of no gaps therebetween by joining mutually adjacent specific base units one after the other in the arbitrary direction in a state of coinciding the face to face of the base units.

CONSTITUTION: Each base unit has the same size twelve rhombus surfaces that is one to 2-1/2 in a ratio of length of the diagonal line, and the angle defined by the adjacent rhombus surfaces and the rhombus surface is 120 degree. In the central part of the base units A, B, C combined together, a recessed groove is formed, and a base unit H is put on the groove. The recessed groove formed in the central part of the base units A, B, C combined together comprises rhombuses having the same configuration and the same dimension in each surface, and has three rhombus surfaces of the angle of 120° defined by adjacent surfaces, and the protrusion of bottom of the base unit H is laid in the recessed part and, similarly, a base I is placed on the recessed groove formed in the central part defined by the base units A, C, D combined together, and the base unit J is positioned on the recessed groove formed in the central part defined by the base units A, E, F combined together. In this manner, the base units can be combined arbitrarily successively, and thereby a three dimensional honeycomb structure can be manufactured readily.