The first experimental evidence of the magnetic quantum oscillation in the photovoltaic effect of Pb1-x Mnx Se p-n junctions is reported. The p-n junctions were obtained in Pb1-x Mnx Se crystals with manganese content ,0 < x < 0.08 by introducing Cd donors by diffusion. Measurements were performed between 5-85 K and in the presence of the magnetic field 0-7 T in the Faraday and Voigt configurations of the incident infrared radiation of various photon energies in the vicinity of the energy gap of a Pb1-x Mnx Se. Strong oscillatory behavior of the photovoltage was observed as a function of the magnetic field intensity at a constant wavelength of the incident light. Using the model of Adler of the energy band structure modified by the exchange terms, and after identification of the initial and final states of the transitions, we derive the band parameters of the Pb1-xM n xS e crystals.