The study of Be stars, characterized by emission lines and rotational velocities close to critical, has long been of interest to astrophysicists. These stars are distinguished by the presence of an equatorial disk, the formation mechanism of which remains unknown. To date, no magnetic field has been detected in any of these stars. The nature of the formation of Be star disks and their magnetism is still not well understood, and explaining them is one of the most urgent and complex problems in modern astrophysics. The star Cassiopeiae ( Cas) is a prominent representative of the small group of Be stars, which have increased X-ray luminosity, corresponding to abnormally high plasma temperatures. This study presents the results of a comprehensive study of the magnetic field of
Cas using archival spectropolarimetric observations obtained with the Main Stellar Spectrograph (MSS) at the 6-m telescope BTA. The results of processing spectropolarimetric observations collected over several years made it possible to estimate the rms field of the star G. The obtained data does not indicate the detection of global magnetic field. We assume that active regions associated with the star's local magnetic fields may be located on the surface of the star. Further research is needed to confirm this result.