A reverse opening slide fastener having a separable bottom end stop comprising: a box pin provided consecutively from a bottom end of a first element row disposed on a side edge of a first fastener stringer; an insert pin provided consecutively from a bottom end of a second element row disposed on a side edge of a second fastener stringer; and an upper slider which enables the slide fastener to be opened upward and a lower slider which enables the slide fastener to be opened in a reverse direction, with rear mouths thereof opposite to each other, the reverse opening slide fastener comprising: a stopper for preventing the lower slider from slipping off, provided at an end portion of the box pin on an opposite side to the first element row; a first engaging portion provided on an opposite side edge of the box pin opposite to the insert pin; and a second engaging portion which engages the first engaging portion so as to position the insert pin in a downward direction, provided on an opposite side edge of the insert pin opposite to the box pin, the upper slider and the lower slider including front and rear blades (52, 54; 62, 64) which form each element row guide passage which allows the first element row and the second element row to pass therethrough, the reverse opening slide fastener being characterized by further comprising a projecting portion (48, 248, 348) which makes contact with an inner face of at least any one of the front and rear blades (52, 54) so as to suppress a free sliding of the upper slider on at least any one of a front side face and a rear side face of the box pin opposite to the inner face of at least any one of the front and rear blades (52, 54) of the upper slider. a box pin provided consecutively from a bottom end of a first element row disposed on a side edge of a first fastener stringer; an insert pin provided consecutively from a bottom end of a second element row disposed on a side edge of a second fastener stringer; and an upper slider which enables the slide fastener to be opened upward and a lower slider which enables the slide fastener to be opened in a reverse direction, with rear mouths thereof opposite to each other, the reverse opening slide fastener comprising: a stopper for preventing the lower slider from slipping off, provided at an end portion of the box pin on an opposite side to the first element row; a first engaging portion provided on an opposite side edge of the box pin opposite to the insert pin; and a second engaging portion which engages the first engaging portion so as to position the insert pin in a downward direction, provided on an opposite side edge of the insert pin opposite to the box pin, the upper slider and the lower slider including front and rear blades (52, 54; 62, 64) which form each element row guide passage which allows the first element row and the second element row to pass therethrough, the reverse opening slide fastener being characterized by further comprising a projecting portion (48, 248, 348) which makes contact with an inner face of at least any one of the front and rear blades (52, 54) so as to suppress a free sliding of the upper slider on at least any one of a front side face and a rear side face of the box pin opposite to the inner face of at least any one of the front and rear blades (52, 54) of the upper slider.