Single crystals of Na2Ca2Nb4O13 were grown by the flux technique and the structure was investigated by the single crystal X-ray diffraction technique with final R/wR factors of 0.052/0.022 for observed 699 reflections assuming the space group Immm with cell dimensions a = 3.885(3), b = 3.884(3), and c = 36.15(3) Angstrom. Layers with formula [(Ca2Na)Nb4O13](-) are concatenated by Na+ cations near the interlayer. The Na+ cations also reside in the intralayer, substituting part of twelve-fold coordinated Ca2+ cations in the perovskite-type unit. The stacking vector of the perovskite-type layer is parallel to the body-diagonal direction, making a clear contrast to that along the face-diagonal direction in the Dion-Jacobson phase with K+ cations residing near the interlayer. A detailed crystallographic study is being in progress, considering a slight structural distortion into base-centred structure.