Abstract: The object of this invention is to provide a milling cutter which includes a cutting insert (120), which has a hexahedral shape and is provided with first and second cutting blade parts on opposite ends thereof, and a cutter body (110) provided with a plurality of insert seats (112) which the cutting insert (120) is seated in and fastened to in either of two directions. The cutting insert (120) is fastened to the associated insert seat (112) in a selected direction, thus all corner blades or main blades, provided on the first and second cutting blade parts of the cutting insert, can be used for machining workpieces. Therefore, the present invention extends the lifetime of the cutting insert (120).