Cyclic oligosiloxane is prepared through disproportionation reaction of organopolysiloxane in the presence of a catalyst. Cyclic oligosiloxane of high purity can be produced in high yields by using a catalyst having formula (4): ##STR00001## wherein M is Al, Ti, Zr, Sn or Zn, p is the valence of M, and R.sup.4 is a monovalent hydrocarbon group or the like.