The purpose of the research was to study the effect of alternating magnetic field on the yield and chemical composition of sugar beet roots. The investigations were undertaken on four varieties of sugar beet viz. Colibri, Evita, Kawetina and Maria and four magnetic exposure doses in the field. The results of the research showed that the effect of the pre-sowing magnetic biostimulation is positive. In all the combinations except Evita variety the yields of roots (5.0-9.4 t/ha) and leaves (5.0-9.4 t/ha) were higher than the yield of control. Also, the biological yield of sugar increased in all the combinations. The alcality coefficient was higher than 1.8, which from the technological point of view, is very advantageous.