  We present the measurements of Faraday rotation for 477 pulsars observed by
the Parkes 64-m radio telescope and the Green Bank 100-m radio telescope. Using
these results along with previous measurements for pulsars and extra-galactic
sources, we analyse the structure of the large-scale magnetic field in the
Galactic disk. Comparison of rotation measures of pulsars in the disk at
different distances as well as with rotation measures of background radio
sources beyond the disk reveals large-scale reversals of the field directions
between spiral arms and interarm regions. We develop a model for the disk
magnetic field, which can reproduce not only these reversals but also the
distribution of observed rotation measures of background sources.
