A door operator of an elevator comprising: a door rail provided above an elevator entrance; a door for opening and closing the entrance; a door hanger for hanging the door; a hanger roller which is provided rotatably on the door hanger to guide the opening/closing movement of the door by means of rolling on the upper face of the door rail; a stabilizing roller which is provided on the door hanger and rotates while being in contact with the lower face of the door rail along with the opening/closing movement of the door; a support body for supporting the door rail, a part of which is arranged along the door rail; and a displacement restraining device which is provided on the door hanger to restrain the door from being displaced to the axial direction of the hanger roller, wherein the displacement restraining device comprises: a first guide roller which rotates while being in contact with one side surface of the part of the support body along with the opening/closing movement of the door; and a second guide roller which rotates while being in contact with the other side surface of the part of the support body along with the opening/closing movement of the door; characterised in that the support body has a plate-shaped member to the side surface of which the door rail is fixed; and the displacement restraining device restrains the displacement of the door by means of the rollers (11,12) brought into contact with the lower end portion of the plate-shaped member arranged along the door rail. a door rail provided above an elevator entrance; a door for opening and closing the entrance; a door hanger for hanging the door; a hanger roller which is provided rotatably on the door hanger to guide the opening/closing movement of the door by means of rolling on the upper face of the door rail; a stabilizing roller which is provided on the door hanger and rotates while being in contact with the lower face of the door rail along with the opening/closing movement of the door; a support body for supporting the door rail, a part of which is arranged along the door rail; and a displacement restraining device which is provided on the door hanger to restrain the door from being displaced to the axial direction of the hanger roller, wherein the displacement restraining device comprises: a first guide roller which rotates while being in contact with one side surface of the part of the support body along with the opening/closing movement of the door; and a second guide roller which rotates while being in contact with the other side surface of the part of the support body along with the opening/closing movement of the door; characterised in that the support body has a plate-shaped member to the side surface of which the door rail is fixed; and the displacement restraining device restrains the displacement of the door by means of the rollers (11,12) brought into contact with the lower end portion of the plate-shaped member arranged along the door rail. a first guide roller which rotates while being in contact with one side surface of the part of the support body along with the opening/closing movement of the door; and a second guide roller which rotates while being in contact with the other side surface of the part of the support body along with the opening/closing movement of the door; characterised in that the support body has a plate-shaped member to the side surface of which the door rail is fixed; and the displacement restraining device restrains the displacement of the door by means of the rollers (11,12) brought into contact with the lower end portion of the plate-shaped member arranged along the door rail.