A simple and reliable locking device for a quick-action connection coupling for transferring gaseous and/or liquid fluids, especially for refuelling vehicles, is provided. Said device comprises a hand lever (50) for actuating a valve and a lock which is positioned on the end side thereof and engages with a hand grip (45) in the refuelling position. To this end, an unlocking lever (46) which can be pivoted on the hand grip (45) is mounted adjacent to the end region of the hand lever (50). The unlocking lever (46) comprises at least one, preferably two laterally protruding journals (47), arranged inside the hand grip (45), especially for simple handling.