The belt lock comprises a closure mechanism and at least one belt strap end piece (2) which can be inserted into the mechanism, the belt strap end piece having a tongue (4) designed to lock with the mechanism. The mechanism has a metal frame (7), an arresting element (8) mounted in recesses (18) in the sides of the frame, an ejector (9) for the tongue, an arresting element support (10) and a belt-release button (11). In order to simplify the belt lock, reduce its manufacturing costs and increase its reliability, the arresting element (8) is designed as a plate with a rear recess (28) and the recesses (18) in the sides of the metal frame are designed as slots in which the arresting element (8) can be mounted. The slots extend parallel to the direction of motion of the tongue (4) in the frame (7) and their size is such that the pins (19) of the element (8) are guided to move in the direction of motion of the tongue (4) substantially without any play at right angles to this direction. The cross-piece part (22) of the frame (7) has a stop (24) which defines the stop location of the arresting element (8), and the arresting element support (10) is located behind the arresting element and above the ejector (9) and can move at least substantially parallel to the direction of motion of the ejector (9).