Adapter device (1) for connecting at least one electrical device (2) adapted for a busbar subsystem (11, 12) to a busbar main system (7), wherein the adapter housing (4) of the adapter device (1) comprises a busbar main interface (22) on a rear side of the housing for electromechanical contacting of busbars (6) of the busbar main system (7) and one or more busbar sub-interfaces on a front side of the housing, which are provided for placing the at least one electrical device (2) on the adapter device (1) and for its electrical connection to the busbar main system (7) via busbars (15, 16) of the respective busbar sub-system (11, 12) integrated in the adapter housing (4) or attached thereto and via electrical conductors (28) contained in the adapter housing (4).