A milling cutter, comprising a cutter body, a cutter holder secured on the cutter body, a cutting insert secured on the cutter holder, and a locking screw extended through the cutter holder and the cutting insert to combine the cutter holder and the cutting insert. Thus, when the locking screw is screwed on the cutter holder, the elastic clamp of the cutter holder is urged to move toward the fixing seat, so that the clamping jaw of the elastic clamp is closely urged on the first end of the cutting insert and the clamping face of the elastic clamp is closely urged on a second end of the cutting insert, thereby locking the cutting insert on the cutter holder rigidly and stably.