A screening device is manufactured relatively inexpensively and easily yet has uniform screening openings even when of a width of less than 0. Each of the Hall effect regions has on the first face a first contact and a second contact that are placed symmetrically with respect to a plane of symmetry at the respective Hall effect region, wherein the plane of symmetry is orientated perpendicular to a straight line between the first contact and the second contact of the respective Hall effect region. The output data from each filter, except the last filter in the sequence, serves as the input data to the next filter in the sequence. The front abutment face is provided at a front end of the coupler, and the rear abutment faces is formed inwardly of an outer side of the coupler.