PURPOSE: To provide a slider with an automatic stop mechanism, which has smooth and beautiful surface shape, by which positioning and operation of a stop claw piece at the time of working and operation can be stabilized and the lateral width of a box-shaped cover body can be reduced as much as possible.

CONSTITUTION: A pair of projections 54 projected inward are provided on a cover body 50 which stores a stop claw piece 30 and a plate spring 40 in the interior thereof, a taper surface 34 corresponding to the projections are formed on a narrow claw piece 30, and at the time of assembling a slider 1, the attitude of a click piece is suitably held by guiding the taper surfaces by the projections to ensure the operation of a stop mechanism. Further, the width of the stop click piece is reduced, the manhour of press working is reduced to minimize a working flaw of the top plate part, and the shape of the cover body 50 is narrow.