PURPOSE: To easily form a three-dimensional structure of composite material by a method wherein composite materials having two-dimensional structure are impregnated with resin and, after that, laminated to one another and hardened and holes are bored on the laminated composite material with ultrasonic and then plugged up with nails, which are made of the same composite material.

CONSTITUTION: Composite materials having two-dimensional structure, each of which is produced by running woof across warp, are impregnated with resin and, after that, laminated to one another so as to form the desired shape. The laminated composite material is put in a high temperature and high pressure tank so as to be turned into semi-hardened state under heat and pressure in order to produce the laminated composite material as shown at the step 3. Nail-shaped matters are produced out of thermosetting composite material by means such as lamination, filament-winding or the like and put in the high temperature and high pressure tank at the step 5 in order to produce nails in semi-hardened state under heat and pressure. Boring is performed in the laminated composite material to the directions normal to the warp and to the woof by applying ultrasonic vibration with an ultrasonic oscillator so as to soften the inner wall of each bored hole, in which the nail is plugged at the step 8 in the directions normal to the warp and to the woof. The laminated composite material under the above-mentioned state is put in the high temperature and high pressure tank at the step 9 in order to fully hardened under heat and pressure.