an apparatus operable on each elevator platform for opening or closing doors wherein the apparatus includes a pair of doors for opening or closing an inlet / outlet on the elevator platform , a rail for guiding the rolling movement of rollers carried by a hanger plate standing upright on the upper surface of each door and a door - sill arranged below said inlet / outlet for guiding the slidable movement of a door shoe at the lower end of each door . each door is essentially composed of a door main body having a vertically extending reinforcement member for supporting the dead weight of each door and a thermal insulating panel fixedly secured to the door main body on the elevator platform side , the thermally insulating panel being filled with a thermal insulating material , and a decorative plate is adhesively secured to the front surface of the thermal insulating panel on the elevator platform side .