The A-site-ordered perovskite YMn3Al4O12 was prepared by high-pressure synthesis. Structural analysis with synchrotron powder X-ray diffraction data and the Mn L-edges X-ray absorption spectrum revealed that the compound has a chemical composition Y3+Mn33+Al43+O122- with magnetic Mn3+ at the A' site and non-magnetic Al3+ at the B site. An antiferromagnetic interaction between the A'-site Mn3+ spins is induced by the nearest neighboring Mn-Mn direct exchange interaction and causes an antiferromagnetic transition at 34.3 K.