X-ray absorption spectroscopy (XAS) spectra near the 0 K-edge of A-site-ordered perovskite with A-site Cu2+ (S = 1/2) spins were measured. The spectra of ferromagnetic CaCu3Ge4O12 and CaCu3Sn4O12 showed hybridization between Cu 3d and O 2p orbitals, but magnetic circular dichroism measurement revealed that the O 2p orbital played a less important role in magnetic interaction. The XAS spectra of antiferromagnetic CaCu3Ti4O12, on the other hand, showed strong hybridization of the Cu 3d, Ti 3d, and O 2p orbitals. These results demonstrated that direct exchange interaction of the Cu2+ spins primarily determined the ferromagnetic ordering of CaCu3Ge4O12 and CaCu3Sn4O12, whereas the involvement of Ti 3d orbitals induced the antiferromagnetic property in CaCu3Ti4O12.