An installation device for a slide assembly includes a first rail and a second rail which has a guide seat and two slots for being connected with an exterior equipment. A positioning member is fixed to the second rail and an arm board has a positioning hole located corresponding to one of the slots of the second rail so that one of installation members of the exterior equipment is engaged with the positioning hole. An end board has a through hole and an end piece extending toward the second rail. The release member is movably installed to the second rail. When the release member is moved by an exterior force and positioned by the guide seat, the protrusion of the release member pushes the end piece to keep the positioning hole away from the second rail and the exterior equipment is removed from the positioning hole.