An object of the present invention is to reduce the time required for the calcination of a lithium metal salt complex to thereby provide a high-quality cathode active material for a lithium ion battery at low cost. The method for producing a cathode active material for a lithium ion battery compirses the steps of: preparing a lithium metal salt solution slurry containing a lithium salt and a metal salt containing an oxidizer or a metal salt containing ions having an oxygenation effect; drying the lithium metal salt solution slurry to obtain a powder of a lithium metal salt complex containing an oxidizer or a powder of a lithium metal salt complex containing a metal salt containing ions having an oxygenation effect; and calcining the powder.
