A miniature linear motion guide unit can eliminate the need for additional machining on a track rail, and thus improve the accuracy of the track rail and reduce the manufacturing costs. A track rail (R) having raceway grooves (4, 5) is fixed to a mounting surface by a fixing member (A). A slider (S) straddles and moves on the track rail. The fixing member has a recessed groove (7) formed in an opposing mounting face (6) facing the mounting surface and straddling the track rail. Part of the recessed groove is in contact with the track rail when the recessed groove straddles the track rail. A mounting hole (11) is drilled in a portion of the recessed groove of the fixing member away from the track rail. A stopper member (10) such as a bolt is inserted in the mounting hole and fixed to the mounting surface.