We have conducted SIMS analyses of siderophile elements (such as PGEs) in metal grains in Y-81020 (CO 3.05) chondrite, and based on the obtained data, we discuss fractionation processes of siderophile elements in the solar nebula. We have analyzed both large isolated metal grains in matrix and small metal grains in chondrules. The analyzed elements were Os, Ir, Pt, Ni, Co, Fe and Au. The major siderophile elements (Fe, Ni, Co) show almost no fractionation relative to CI composition. On the other hand, refractory siderophiles (Os, Ir and Pt) show significant variations in their abundances from unfractionated to highly depleted by a factor of 100. Such a large depletion in refractory siderophiles may suggest a high temperature fractionation process, in which metal grains formed from the gas after removal of the most refractory siderophiles.