The present invention relates to a connecting device (9) for connecting an adjacent first and second panel (10, 20) along facing sides (19, 29) in a spaced relationship, the first panel comprising opposite first and second faces (11, 12), the second panel comprising opposite first and second faces (21, 22). The connecting device (9) comprises a first and a second part (1, 2), the first part (1) being provided for mounting to the first face (11, 21) of the first and second panel and the second part (2) being provided for mounting to the second face (12, 22) of the first and second panel (10, 20) opposite the first face (11,21), the first and second part (1, 2) respectively comprising first and second connecting means (4, 5) which are provided to mutually engage each other in view of connecting the first and second part (1, 2). The connecting means extend within a space (3) between the first and second panel (10, 20). The first part (1) comprises a first and second wing (13, 14) on opposite sides of the first connecting means (4) and the second part (2) comprises a third and fourth wing (23, 24) on opposite sides of the second connecting means (5), the first wing (13) being provided to co-operate with the third wing (23) upon connecting the first and second part (1, 2) in view of forming a first space (38) for holding the first panel (10) therebetween, the second wing (14) being provided to co-operate with the fourth wing (24) upon connecting the first and second part (1, 2) in view of forming a second space (39) for holding the second panel (20) adjacent to the first panel (10) therebetween, the first and second space being positioned on opposite sides of the connecting means (4, 5).