suitably selected to permit the cutting edge defined by the upper edge of each of the recesses to be formed into a desired length the recesses each are preferably formed into a circular shape from the viewpoint of manufacturing of the strainer for example the recesses may be formed into a diameter of about 20 to 150 mm and a depth of about 0 5 to 5 0 mm alternatively the recesses may be formed into any suitable shape such as an elliptic shape a rectangular shape a triangular shape or the like other than a circular shape the strainer of the present invention may be manufactured according to any suitable process other than the above described process for example it may be manufactured by subjecting a single plate material to cutting to form the recesses and then forming the plate with the straining apertures alternatively it may be produced by superposing a plate formed with through holes corresponding to the recesses and a blank plate on each other and then forming the plates with the straining apertures as can be seen from the foregoing the strainer of the present invention for paper making which is arranged in the vicinity of a rotor for screening a paper feedstock macerated is formed with a plurality of the recesses on the surface thereof opposite to the rotor to thereby eliminate the mounting of cutters on the strainer as required in the prior art resulting in effectively preventing.