Known oscillating motors tend to present scaling problems; in particular they are often inadequately sealed in relation to the outside. The scaling elements also have a short service life as a result of the considerable strains to which they are subjected. The invention therefore provides an oscillating motor whose annular sealing ring consists of a sliding sealing ring (23) and a soft sealing ring, said rings being positioned next to each other on a common axis. The soft sealing ring is configured as a diagonal sealing ring (28) and is located on the sides of the pressure or discharge chambers (13, 14). The sliding sealing ring (23) is configured so that it is torsionally rigid in relation to the rotor (2). For this purpose, it preferably has two axial grooves (32), said grooves being arranged so that they are parallel and in pairs. The grooves (32) correspond to driver elements (31) located on the rotor wings (10).