Magnetic fields are an important agent for cosmic rays to transport. The observed all-sky Faraday rotation distribution implies that the magnetic fields in the Galactic halo have a toroidial structure, but the radius range and scale height as well as the strength of the toroidial fields are totally unknown. In the Galactic disk, the magnetic fields probably follow the spiral structure with a strength of a few microGauss and several large-scale reversals in the arm and interarm regions, as inferred from the rotation measure distribution of pulsars inside our Milky Way and from the rotation measure difference between distant pulsars and the radio sources behind the Galactic disk. See Han JL (2017, ARA&A 55, 111) and Han JL et al. (2018, ApJS 234, 11) for details.