We present radio continuum polarimetry observations of a nearby edge-on galaxy which posses a very bright radio halo. Using vertical synchrotron emission profiles we have determined the cosmic ray bulk speed as $280\,\rm km\,s^{-1}$ indicating the presence of a galactic wind in this galaxy. The large-scale magnetic field was decomposed into a toroidal component in the disk and a poloidal component in the halo. The poloidal component shows a prominent ``X''-shaped magnetic field structure centered on the nucleus similar to the magnetic field observed in other edge-on galaxies. Hence, NGC 253 offers the possibility to compare the magnetic field structure with models for galactic dynamos and for flow patterns of galactic winds. For this we also analysed the line-of-sight component of the magnetic field using the Rotation Measure.