To provide an opposed-jet impact type jet mill having a cover gap (the gap between the lower end face of a classification rotor of a cover of the mill and the opening of a pulverized and classified powder conveyance means of a main body of the mill) adjustment device, which is capable of being used for pulverization, classification, etc., of a powder and easily performing adjustment of the above gap and also by which a pulverized and classified powder hardly contaminated with impurities can be obtained.

This mill is provided with: a cover 20 having a classification rotor 4 which is used for classifying a raw material powder pulverized with high-pressure gas streams opposed to each other and connected to a main body of the cover 20 in a upwardly and downwardly movable manner and provided at its lower end with a flat face 4f perpendicular to a rotary shaft 4b and also with an exposed flat face 4a that is positioned outside the main body of the cover 20 so as to be opposite and parallel to the face 4f; a pulverizer main body 10 having within it, a powder conveyance means 5 which is provided with an opening 5a that is formed opposite and parallel to the face 4f and used for introducing the powder classified with the rotor 4, and intended for conveying the power introduced through the opening 5a; and a displacement measurement means 30 for measuring the distance between the means 30 itself and the exposed flat face 4a and determining the difference of the measured distance from an initially set distance.