To provide a method for fining the internal structure of a material by applying very large twist strain to the solid material and the powdery material of metal or high polymer, etc.

The lower end surface in contact with a die, of a hollow container having penetrated inner surface grooves, is the plane face at the right angle with the center axis of this container, and the lower end surface of this container and the upper surface of the die, in which the upper part and one of the lateral part are the grooves released to a space at the upper part and at the right angle direction thereto, respectively, and the upper surface is formed so as to become the flat surface, are mutually brought into contact and disposed so as to be mutually communicated with these groove parts. Successively, in a twist-lateral extruding working method, the extruding working of the material from this die groove part toward the lateral part at the right angle to the center axis, is performed while fixing the die so as not to rotate to a frame base and rotating the container around the pushing-in axis.