Ceramic sheets of Na3V2(PO4)3 (NVP) with NASICON-related structure have been prepared by tape-casting method. The addition of 60Na2O-10Nb2O5-30P2O5 glass to NVP is demonstrated to enhance markedly the density of the sintered NVP sheet and its electrical conductivity. The best densified NVP sheet with a thickness of a few tens of μm is obtained by sintering tape-casted NVP added with 5 wt% glass at 920 °C, which exhibits a total conductivity of 2.9 × 10−5 S cm−1 at room temperature. A Pt | NVP sheet | Pt cell works as a tiny solid-state battery with a cell potential of 1.7 V, in which NVP acts as both cathode and anode active materials via redox reactions of V4+/V3+ and V3+/V2+ as well as a Na+ ion conducting electrolyte between the two electrode layers.