A switch adapter is integrateable into a seat belt lock and used for monitoring the locking and unlocking state of the lock. The switch adapter includes a monolithic plastic part and is at least two adapter areas which are movable with respect to each other. The first adapter area carries a first switch element and the second adapter area carries a second switch element. The switch adapter is suitably integrateable into the lock of the seat belt which is provided with a frame and a locking element which is movably mounted so as to switch the seat belt buckle between a locking position and an unlocking position. The switch adapter is used for detecting the locking state of the seat belt locking element. For this purpose, the switch adapter and the locking element are actively connectable to each in such a way that the switching state of the switching adapter and the position of the locking element are modifiable only simultaneously.