A novel A-site ordered perovskite CaCu3Pt4O12 was synthesized under high pressure and high temperature of 12 GPa and 1250 degrees C. CaCu3Pt4O12 is the first perovskite in which the B site is fully occupied by Pt4+. The crystal structure refinement based on the synchrotron powder X-ray diffraction data shows that CaCu3Pt4O12 crystallizes in the space group Im (3) over bar (cubic) with a lattice constant of a = 7.48946(10) angstrom. The magnetic susceptibility data show the antiferromagnetic transition at T-N = 40 K, which is attributed to the magnetic ordering of Cu2+ spins with S = 1/2.