Screening apparatus, concentrating system, dewatering system, and water treatment system

A screening apparatus (1) comprises a cylindrical body (2A) that includes a plurality of strips (3A) and that has a predetermined inner diameter; four restricting units that restrict movement of one end and the other end of each of the plurality of strips (3A) outward and inward in a diameter direction of the cylindrical body (2A); an annular sliding unit (4A) that is arranged at one end of the cylindrical body (2A); and a controlling device that rotates the annular sliding unit (4A) around a center axis (O). The inner side of the annular sliding unit (4A) has a shape formed by alternately and regularly repeating a convex part (43a) and a concave part (44a) protruding and depressing with respect to the center axis (O). The controlling device can widen an aperture formed between two neighboring strips (3A) on the one end to be larger than an aperture formed between the neighboring strips (3A) on the other end by rotating, under a state where the predetermined inner diameter of the other end of the cylindrical