Abstract: A developing device includes a developing section provided with an applicator for applying a developer to a latent electrostatic image and a supporting section for supporting the developing section turnably between an operating position at which the developer held on the applicator acts on image-bearing member and a non-operating position at which the developer held on the applicator does not substantially act on the image-bearing member. According to a first aspect, positioning device acts on the developing section and holds it at the operating position. According to a second aspect, there is provided device for holding the developing section at the non-operating position at the time of mounting a main body of the developing device on an image-forming machine. According to a third aspect, when the main body of the developing device is mounted on the image-forming machine, electrical connecters provided thereon are electrically coupled to each other.