Abstract: In a screen device for a paper material which includes a substantially cylindrical housing equipped therein with a raw paper material inlet at its one end and with a refined paper material outlet and an impurity outlet at the other end, a cylindrical screen member disposed in said housing so as to divide it into an exterior chamber communicating with said raw paper material inlet and with said impurity outlet, and an interior chamber communicating with said refined paper material outlet, and a screen surface-cleaning mechanism disposed in such a manner as to rotate with a small gap between it and the screen surface of said screen member; the improvement wherein the screen open portions of said screen member are shaped into continuous slant slits, the slant angle is brought into substantial conformity with the flowing direction of the paper material flowing on the screen surface and the end slits on the downstream side in the passing direction of the paper material through the screen are left open.