A passenger boarding bridge comprising: a tunnel unit including a walkway; a cab rotatably provided on a distal end of the tunnel unit; a drive wheel provided on the tunnel unit or the cab; a rotational mechanism configured to rotate the cab; a controller configured to control the drive wheel to move the cab, control the rotational mechanism to rotate the cab such that the cab is in an orientation in which a distal end part of the cab faces an entrance of an aircraft, and cause the distal end part of the cab to be docked with the entrance; an entrance image capturing camera mounted to the cab and configured to capture an image of the entrance of the aircraft; and an entrance position calculator configured to detect the entrance of the aircraft based on the image of the entrance, which is captured by the entrance image capturing camera, and calculate horizontal positional information of the entrance, wherein the controller is, when the cab is at a predetermined standby position from which the cab starts moving at a time of performing docking of the cab with the entrance, configured to: calculate a target position based on the horizontal positional information of the entrance, which is calculated by the entrance position calculator, the target position being a destination position to which the cab is moved for docking the cab with the entrance; and move the cab from the standby position to the target position; wherein, during movement of the cab from the standby position to the target position, the control device is configured to monitor the image captured by the entrance image capturing camera and to stop the passenger boarding bridge from moving if the entrance stops being shown in the captured image; wherein the target position is a position of the cab at which the cab is spaced apart forward from the entrance by a predetermined distance, and characterised in that the controller is further configured to: when the cab has reached the target position, calculate a docking position based on the horizontal positional information of the entrance, which is calculated by the entrance position calculator, the docking position being a position at which the cab is docked with the entrance; and move the cab to the docking position, and stop the cab at the docking position. a tunnel unit including a walkway; a cab rotatably provided on a distal end of the tunnel unit; a drive wheel provided on the tunnel unit or the cab; a rotational mechanism configured to rotate the cab; a controller configured to control the drive wheel to move the cab, control the rotational mechanism to rotate the cab such that the cab is in an orientation in which a distal end part of the cab faces an entrance of an aircraft, and cause the distal end part of the cab to be docked with the entrance; an entrance image capturing camera mounted to the cab and configured to capture an image of the entrance of the aircraft; and an entrance position calculator configured to detect the entrance of the aircraft based on the image of the entrance, which is captured by the entrance image capturing camera, and calculate horizontal positional information of the entrance, wherein the controller is, when the cab is at a predetermined standby position from which the cab starts moving at a time of performing docking of the cab with the entrance, configured to: calculate a target position based on the horizontal positional information of the entrance, which is calculated by the entrance position calculator, the target position being a destination position to which the cab is moved for docking the cab with the entrance; and move the cab from the standby position to the target position; calculate a target position based on the horizontal positional information of the entrance, which is calculated by the entrance position calculator, the target position being a destination position to which the cab is moved for docking the cab with the entrance; and move the cab from the standby position to the target position; wherein, during movement of the cab from the standby position to the target position, the control device is configured to monitor the image captured by the entrance image capturing camera and to stop the passenger boarding bridge from moving if the entrance stops being shown in the captured image; wherein the target position is a position of the cab at which the cab is spaced apart forward from the entrance by a predetermined distance, and characterised in that the controller is further configured to: when the cab has reached the target position, calculate a docking position based on the horizontal positional information of the entrance, which is calculated by the entrance position calculator, the docking position being a position at which the cab is docked with the entrance; and move the cab to the docking position, and stop the cab at the docking position. when the cab has reached the target position, calculate a docking position based on the horizontal positional information of the entrance, which is calculated by the entrance position calculator, the docking position being a position at which the cab is docked with the entrance; and move the cab to the docking position, and stop the cab at the docking position.