A belt lock (8) for receiving an attachment element (2) of a safety belt (1) has an insertion opening (10) for the attachment element (2). In the belt lock (8), a connection element (20) is provided, which penetrates a locking opening (3) on the attachment element (2). The connection element (20) is disposed on a flat spring-type carrier (17), via which an insertion movement (24) of the connection element (20) into the locking opening (3) of the attachment element (2) takes place, when the attachment element operates a locking lever (12) by its insertion movement. The insertion movement (24) of the connection element (20) is monitored via a magnetic circuit containing a magnetic field-sensing sensor (31). A component (11, 20) of the belt lock (8) that fixes the attachment element (2) of the safety belt (1) is associated with a measuring element (20), with which a force operating on the belt lock can be determined via the magnetic circuit (16, 31).