Abstract: Providing an overturn preventing device which can be easily mounted at an appropriate inclination angle. The overturn preventing device includes a damper, a pair of bases, and an angle regulator. The damper is mounted between a top surface of a piece of furniture installed on an installation surface and a ceiling. Both ends of the damper are respectively coupled to the bases so as to be rotatable about respective rotation axes. The first base abuts against the top surface of the furniture and the second base abuts against the ceiling. The angle regulator is attached to the first base. The angle regulator regulates an inclination angle of the damper.