A rotary laser (1) has a laser beam unit (7) which is suitable for emitting at least one laser beam (2) rotating in a beam plane (E) and which is controlled by computer (9) so as to be switchable from a rotating operating mode (I) in which the at least one laser beam (2) rotates in the beam plane (E), to a scanning operating mode (II) in which the at least one laser beam (2) scans in the beam plane (E) within an angular sector (.phi.), and a plurality of detectors (10) distributed circumferentially around an axis of rotation (A) and which are sensitive to an amplitude at least within the beam plane (E) and are connected to the computer (9).