For achievement of a reduction in size, a slider unit comprises a mounting base 1, a rail 2 fixed to a mounting face 1a of the mounting base 1, a slide table 3 moving along the rail, position detection means for detecting the position of the slide table 3, and a driving system for moving the slide table 3. The mounting face 1a of the mounting base 1 has a mounting recess 14 formed therein. A sensor board 16 on which a Hall element 16a is mounted is installed in the mounting recess 14. The slide table 3 has a permanent magnet 19 attached to the face thereof facing the mounting face 1a. The permanent magnet 19 and the Hall elements 16a form the position detection means.