Fastening device for safety belt

The device has a lug-shaped cam, and a receiving device (20) for receiving a plug-in unit. A locking device (30) retains the unit to secure a belt. The device (30) is formed by a single-part closure spring that is secured in/on the device (20). The spring is formed by a spring plate that is bent apart, when the unit is inserted into the device (20). An end fitting tightener is provided between an end fitting lock and a vehicle chassis. The lug shaped cam securely locks the plug-in unit by side regions of the closure spring that cause latching to be securely and permanently pressed against side flanks of the plug-in unit, after locking has taken place.