First (after the Sun) astronomical objects with measured magnetic fields were CP stars. Now there're more than 350 stars known to be magnetic CP ones, it is the most numerous group of stars with measured magnetic fields. Number of stars is descreasing by exponential law from the detection limit to tens of kG. There's a weak dependence: hotter and and faster rotating stars have stronger fields. The observational data give an evidence on the relic nature of the magnetic field of these objects. Depressions in the continua of CP stars are observed, intensity of depressions correlates with magnetic field strength. Chemical composition is anomalous, the distribution of elements is non-uniform. Observations confirmed efficiency of magnetic separation mechanism in the atmospheres of CP stars. Detail study of Zeeman effect gives us new possibilities for searching physical processes in the atmospheres of magnetic stars.