A jet mill in which crushed material introduced into a crushing chamber is comminuted by gas being sprayed from a plurality of gas-jet nozzles, wherein high-efficiency pulverization is performed by optimizing various pulverization conditions according to the type of crushed material or other such properties. The direction in which gas is sprayed into the crushing chamber is variable adjustable; the spraying direction of each nozzle is displaced simultaneously by the electromotive actuator; swirl flow is produced in three dimensions, including the flow of a directional component that is perpendicular to the horizontal swirl flow; and a fine-powder discharge port of a first pulverization chamber and a fine powder introduction port of a second pulverization chamber are communicatingly connected by a ventilation duct.