A connecting device (10) is provided for releasably connecting a fitting piece, such as an interior lining, to a supporting structure, such as a fuselage. The connecting device (10) includes a plug-in holding mechanism (50) including a bushing piece (52) and a connecting pin (75) that can be releasably locked therein. A bent connecting arm (60), to which the connecting pin is fastened, is releasably fastened to a structural holder (40) mounted on the supporting structure. In one position, the connecting arm (60) is plugged into the structural holder (40) and is releasably locked therein. In a second position (125), in which the connecting arm (60) is rotated 180° about the longitudinal axis thereof, an electrical contact device (90) is additionally inserted between the connecting arm (60) and the bushing piece (52). Hence, the same structural holder (40) and the same connecting arm (60) allow the fitting piece and the supporting structure to be connected to one another with or without connecting a contact device (90) therebetween.