Disclosed is a process for the preparation of metallocone complexes wherein stereoisomers of metallocene complexes formed at the time of synthesis can easily be separated. The gist of the present invention resides in separation of a part of an isomeric mixture of specific metallocene complexes bridged with a transition metal represented by the formula (1) as a complex having M—O bond. In particular, preferable is a process for separating a part of an isomeric mixture of a metallocene complex represented by the formula (2) as a &mgr;-oxo-complex represented by the formula (3).