A coupling apparatus having a device for automatic connection of power lines, in particular of hydraulic lines, for the attachment of working tools to a tool mount of a excavator boom by means of a quick-action coupling, wherein, in order to connect the tool mount to the working tool, the quick-action coupling has a hook connection and a blocking unit with a movable bolt element which is operated by an actuating unit. Supply connecting pieces are fixed to the tool mount, and the corresponding power take-off connecting pieces of the working tool are fixed on a mount, which is mounted on the working tool such that it can move between a moved-forward position and a drawn-back position, wherein the mount has a driver piece for engagement with an operating element which is coupled to the movable bolt element. When the blocking unit is closed, the power take-off connecting pieces are connected to the corresponding supply connecting pieces and, when the blocking unit is open, they are detached from the supply connecting pieces.