Provided is an attachment structure of an opening adjusting device. The attachment structure prevents other parts of a vehicle from being damaged by an opening adjusting device during bumping. The attachment structure of an opening adjusting device (100) is disposed in an airflow channel into which travelling wind is directed through an opening O provided in a bumper face (40). A movable louver blade (120) driven by an actuator (130) substantially opens and closes the airflow channel. An upper part of the opening adjusting device is disposed to face a rear wall of the bumper face and is attached to a bumper beam (50) extending substantially along a vehicle width direction. A lower part of the opening adjusting device is either one of attached to a vehicle body structural member (20) and a load transmission member (60) projecting forward from the vehicle body structural member. The upper part of the opening adjusting device and the bumper beam are connected with each other with an upper bracket (140) having a weak portion (144) that is configured to be broken in response to pivotal movement of the opening adjusting device relative to the bumper beam.