This book presents a comprehensive account of the magnetic fields of various celestial bodies -- the Sun, the Moon, planets, stars, the Milky Way, and galaxies as well as the interplanetary, interstellar and intergalactic media. The original Chinese edition was published in Beijing in 1978. The present English edition has been greatly enhanced, much improved and thoroughly rewritten. Compared with other books published in the same field, this monograph is mainly characterized by the completeness and freshness of its contents. It may be used as a reference and textbook for scientific researchers and students of astronomy, space physics, geophysics and other related sciences.