The utility model discloses a numerically-controlled vertical milling cutter which comprises a cutter bit, a cutter rest, a compression device and positioning holes, wherein the tail end of the cutter bit is provided with the positioning holes formed in two rows and night lines, the compression device is composed of a tight set block, a spring and a lock screw, the spring is arranged between the tight set block and the lock screw, the compression device locks the cutter bit on the cutter rest through the bonding force of the tight set block and positioning holes, one end, fastened with the cutter bit by locking, of the cutter rest is provided with a hollow cavity, the wall of the hollow cavity of the cutter rest is provided with through holes corresponding to the positioning holes formed in two rows and night lines, and the milling cutter is structurally characterized in that a transition groove communicated with a positioning hole is arranged beside the positioning hole of the cutter bit, and a drop-proof groove communicated with the transition grooves in a same line is arranged above the transition grooves in a same line.