The reverse opening type slide fastener has a separable bottom end stop including upper and lower sliders, wherein a stopper for preventing the lower slider from slipping off is provided at the bottom end of a box pin. A first engaging portion is formed on an opposite side edge opposite to an insert pin of the box pin and a second engaging portion is formed on an opposite side edge opposite to the box pin of the insert pin to position the insert pin in a downward direction when the second engaging portion engages the first engaging portion. A projecting portion which makes contact with the inner face of the blade of the upper slider to suppress a free sliding of the upper slider, is formed on at least any one of front and rear side faces opposite to the inner face of the blade of the upper slider of the box pin.