Abstract: In a separable bottom stop assembly of a concealed slide fastener, U-shaped guide portions are respectively connected continuously to ends of inner side edge of a box pin and a separable pin both in a shape of a prism for guiding flanges of the box having at a front face thereof an opening portion. Flat support portions are connected continuously to outsides of the guide portions, and the guide portions and the support portions made of thermoplastic resin are integrally molded to bottom ends of fastener stringer tapes. The guide portions and the support portions connected continuously to the box pin and the separable pin are thin at their portions where the box is disposed and thick at their portions outside the thin portions. The thick portions of the support portions extend to one-side faces of the fastener tapes. The box pin can be inserted into and fixed to a box-pin-insertion hole of the box.