To develop a new machining technique that will give an accurate direction to fibers in a polymer component material.

Regarding a method and a device for inserting a material into a base material, the present device 10 has a needle assembly 10 having a needle 14, a central part 26 being movable and an upper end part 28 being fixed substantially. The material 17 to be inserted is put in the needle 14 through the device 10 and cut in a desired length by a cutter 18. When the needle 14 is put into the base material, the subsequent portion of the material 17 is sent into the device 10. When the needle 14 is extracted from the base material 12, this subsequent material is pressed in the needle 14 and the cut portion 16 is left in the base material. In the method using this device, an additional stage of giving an angular direction to the device and a stage of controlling the degree of concentration of the inserted material in the base material may be provided.