This book highlights fundamentals and advances in the theories and observations of solar magnetic fields. Solar magnetism is an important part of solar physics and space weather research. It covers the formation, development, and relaxation of the magnetic fields in the solar eruptive process. The book discusses topics ranging from measurement facilities for solar observations to the evolution of solar magnetic fields, the storage of magnetic energy, and the magnetic helicity in the solar atmosphere and its relation with solar cycles. The book also presents recent advances in measurements and observations of solar magnetic shear, currents, magnetic helicity, and solar cycles. The book intends for astronomy-majored students and researchers interested in solar magnetism and its role in astrophysics.