PURPOSE: To efficiently preform a hole of desired size in a fiber-reinforced composite material by translationally moving a rotation symmetrical milling body to an edge of the hole while rotating the same with respect to its axis.

CONSTITUTION: A rotation symmetrical milling body 3 is inserted into a preformed hole 2. On this occasion, the axis of rotation of the milling body 3 is oriented perpendicularly to the longitudinal direction of the fiber of a laminated board 1, that is, perpendicularly to the board plane. The hole 2 is machined by translationally moving the milling body 3 along the edge of the hole while rotating the milling body 3 relative to the axis 5, whereby the existing damages and defects 6 are removed. The size and form of a finished hole 7 are substantially different from those of the preformed hole 2. That is, the finished hole can be provided with the desired form and size, and it should have the form and size needing the deletion of the material for removing at least the existing damages and defects by the machining by the milling cutter.