Transmission electron microscopy (TEM) analyses were performed to examine the spontaneously ordered structure in single crystals of 3.2 mole% of Y2O3 added ZrO2 (3.2 YSZ) manufactured by the Skull melting method. The selected area electron diffraction patterns showed several super-structure reflections with symmetrical intensity at (100), (010), and (110) positions, indicating that Y0.5Zr0.5O(2-x) with L1(0)-like cation-ordered structure was formed in 3.2 YSZ. High-resolution TEM has been used to reveal the presence of the partially ordered structure, which was characterized by a doublet periodicity in the contrast of the {100} lattice planes.