PURPOSE: To reduce the clogging of a screen while enabling the separation of a fine powder and to enhance the efficiency of the separation work of a powder and the accuracy of the particle size of the separated powder by automatically detecting the state of the clogging of the screen and the damage thereof.

CONSTITUTION: A powder separator is constituted of a screen 1 circulated or shaked at a predetermined position, the powder jet orifice 2 provided on one surface side of the screen 1, the fine powder suction port 3 provided in opposed relation to the powder jet port 2 through the screen 1, the coarse powder suction port 5 provided at the position where the screen l advances in adjacent relation to the powder jet orifice 2, the cleaning fluid jet orifice 4 opposed to the coarse powder suction port 5 through the screen 1 and a detection means 6 detecting the state of the screen 1.