The north-south asymmetry of the amplitude of ULF pulsations in the Pc 3--5 band is studied using magnetic field data from the magnetically conjugate stations at L ~ 5.4: Kotzebue (KOT) in the northern hemisphere and Macquarie Island (MCQ) in the southern hemisphere. We obtained the following results for the northward (H) component of magnetic pulsations: (1) The north to south power ratio shows a maximum in the northern winter and a minimum in the northern summer. This seasonal variation is stronger at higher frequencies (Pc 3 and Pc 4 frequencies). (2) The north to south power ratio for the Pc 4 and Pc 5 frequency band is basically greater than 1.0 for all seasons. This positive offset is stronger at lower frequencies. The seasonal variation implies that the magnetohydrodynamic (MHD) waves incident from the magnetosphere are more strongly shielded when the ionospheric conductivity is higher. The positive offset may result from the difference of the background magnetic field intensity between KOT and MCQ.