A locking device and a headrest are disclosed. The locking device includes spring elements, which can be engaged in at least one locking position and the locking device can be displaced in relation to at least two retaining bars that have a large number of recesses. The spring elements co-operate with the recesses in such a way that the engagement of the spring elements in their locking position locks the locking device in relation to the retaining bars. According to the invention, the spring elements are configured in such as way that the retaining bars are locked by the mechanical fixing of the spring elements in their central zone or by exertion of a force on the spring elements in their central zone.