A connecting unit for a flat wiper blade is provided. The connecting unit separably connects the flat wiper blade to a wiper arm having one of the following: a first coupling element including a top plate and a pair of side plates having a concave portion at a rear end; a second coupling element including a top plate and a pair of side plates; and a third coupling element including a side pin and a clip arm. The connecting unit has a bracket fixed to a frame of the flat wiper blade and an adaptor. The adaptor is pivotally mounted on the bracket via a pivot shaft of the bracket. The adaptor has first to third fixing devices separably fixing the adaptor to the first to third coupling elements respectively. The flat wiper blade is connected to the wiper arms via the adaptor.