The effect of a magnetic field on the viscosity of the gelatin-water system at different pH of the medium is studied. For the first time it is shown for a polyelectrolyte - solvent system that the magnetic field increases the viscosity of the system by 1.5 times at pH = 7.2, but decreases the viscosity of the system by 2.5 times at the isoelectric point at pH = 4.7.