We determined the magnetic phase diagram of UPd 3 with the hexagonal structure. There are three successive phase transitions at 7.5, 6.8 and 4.5 K. This first transition is due to the quadrupolar ordering, which was qualitatively discussed on the basis of the quadrupolar interaction with the order parameter O zx . The de Haas–van Alphen experiments were also done to clarify the Fermi surface property.