The magnetic field is common in space. The strength and configuration of the field vary in a wide range, and its role could be dominant in many astrophysical processes. Stellar magnetic fields are observed everywhere in the Main Sequence, but only in the small group of chemically peculiar stars, these fields reach their maximum value up to 30 kG making such stars the strongest non-degenerated magnetic objects in the Universe. This talk is devoted to the methods and results of the study of stellar magnetic fields. I will explain the difference between various types of stars hosting the field, introduce the observational techniques. Special attention will be paid to the latest results and their impact on different fields of astrophysics.