New platinum(IV) complexes which has a strong antitumor activity and has a feature that a side effect is relatively reduced is provided. The new complex is platinum(IV) complexes with cis,cis-spiro[4,4]nonane-1,6-diamine ligand and is platinum(IV) complexes with optically active cis,cis-spiro[4,4]nonane-1,6-diamine ligand. Especially, the new complex is dichloromalonato((1S,5S,6S)-spiro[4.4]nonane-1,6-diamine)platinum(IV).