The aim of this research was to study the influence of magnetic field on the growth of microorganisms. In our experiments this influence was tested using Escherichia coli strain BT21. The experiments were carried out in a shaker flask at different intensities of magnetic field. The application of magnetic drives and joints in the bioreactors imposes strong requirements on the hermetic sealing of the testing vessels, which is utterly important from the sterility point of view. Our experiments have convincingly shown that the magnetic influence results in higher growth rate of biomass. In addition, some indications have been obtained that as the magnetic strength exceeds a definite level its positive influence on the bacterial growth decreases.