To provide an encoding method for a three-dimensional shape whereby not only the three-dimensional shape can be expressed without depending on a coordinate system but also the shape can be expressed by simple rows of 0 and 1 so that description of positional relationships concerning tetrahedrons is simplified to reproduce a way of folding from the rows of 0 and 1 without the need for expertise.

The fundamental element of a three-dimensional shape is a tetrahedron composed of triangles each with its three sides having a ratio of 2:√3:√3 in length. The tetrahedron 3 connects with a following tetrahedron 4 at their common long side 8. 0 and 1 are allocated to two sides which can make contact with each other when the tetrahedrons are rotated using the long side 8 as an axis. Rows of 0 and 1 obtained when some surfaces of contact are brought into contact are arranged so that a value for the tetrahedron 3 at the top end assumes the lowest bit. The value is displayed in hexadecimal whereby description of the positional relationships concerning the tetrahedrons 3, 4 is simplified to reproduce a way of folding from the rows of 0 and 1 without the need for expertise.