&Physics of Stars and Interstellar Medium BRussian Kstellar spectra// The computer code SynthM of spectrum synthesis in magnetic stellar atmospheres under the assumption of LTE in plane-parallel atmosphere is described. The comparison of calculated Stokes IQUV shows good agreement between SynthM and N. Piskunov's SynthMag codes. We carried out test calculation of synthetic profiles of selected lines observed in spectrum of β CrB. SynthM code allows one to calculate synthetic spectra with present abundances stratification. The code allows us to use two built-in analytical models of stellar magnetic field configuration. Also, it is possible to use arbitrary model of magnetic field configuration by setting the modulus and direction of field for each integrating node of a surface grid.