Abstract. A magneto-optical trap of metastable 3He atoms has been demonstrated. Some 105 atoms have been confined in a region with a diameter of 0.4mm at a temperature of 0.5mK; the atomic number density is estimated to be 109/cm3 at the trap center. These characteristics of the 3He trap are almost comparable to those of the 4He trap so far demonstrated by many workers. By monitoring the fluorescence from the trap, the trap loss rate has also been measured and discussed.