At both sides of a pair of doors 10L, 10R, a pair of television cameras (two-dimensional image sensors) 18A, 18B for detecting a moving object, and a pair of spare infrared ray sensors 20A, 20B are provided. A central control unit 16 calculates the position and moving direction of moving object by image processing of outputs of television cameras 18A, 18B, and predicts the passing position of moving object on the vertical plane P when the moving object approaches, thereby calculating the target opening degree of a pair of doors 10L, 10R individually, and determines the target opening degree of doors in full closing when the moving object leaves away, and thus outputs move command signals to motor controllers 14L, 14R so that the pair of doors 10L, 10R may be set at the target opening degree.