According to an embodiment, a measuring device for measuring a laser beam comprises a magnification lens system with a total of two lenses which are arranged in series in the beam path of the laser beam and whose foci are coinciding, as well as a camera which is arranged behind the two lenses in the focus of the last lens and includes an electronic image sensor which generates an electronic image of the magnified laser beam. The lenses together with the camera are adjustable along the beam path relative to a reference point of the measuring device, for the purpose of locating the beam waist of the laser beam and of determining a diameter profile of the laser beam. The measuring device further comprises an adapter enclosing the beam path for coupling the measuring device to a laser system which provides the laser beam. The adapter forms an abutment surface or the laser system, which is axially directed with respect to a beam axis of the laser beam, and permits the measuring device to be coupled in situ at the installation site of the laser system.