A slide fastener includes a pair of first and second separable interfitting parts fixed to first and second fastener stringers. The first separable interfitting part includes a slider-holding part, and the second separable interfitting part is configured to be insertable/removable into/from the slider held on the slider-holding part through the tape insertion gap. A protruding part is arranged at a front end of the second separable interfitting part. A width dimension A of the protruding part, a dimension B between a back end of a side surface of the protruding part and an opposed end on a side opposite to the first separable interfitting part, and a dimension C between a guide post and a flange of the slider have a relationship of A