An attachment device for attachment of an electrical or electronic device to a top-hat rail, including an attachable or integrated carrier plate, and a lockable fastener. The carrier plate has a holding device. The fastener is axially movable relative to the carrier plate and has an elongated base region, metal catch hooks, and a spring tongue punched out of the base region. The carrier plate has a projection protruding in a direction of the fastener, and arranged corresponding to the spring tongue. In a mounted state, the spring tongue is deflected by the projection so that the catch hooks are pulled against the top hat rail by a reset force thereof