To provide a method for increasing twisting strain over the full length of material when the inner structure of the material is to be micronized by applying a large twisting strain to a solid material and a powder material such as metal and polymer.

When the material loaded inside a container 3 is pushed in by a pusher 4 farther and subjected to extrusion forming with an inner die 2 having an open cavity 2-1, either the container 3 or the inner die 2 is fixed not to rotate in the rotational direction, while the other is rotated around the extrusion axis, in the twist forward extruding method. In the method, an entry side edge face of the portion of inner die 2 which is enclosed inside the container 3 is equipped with projected and recessed faces 2-2 other than the open cavity 2-1.