It has been considered to apply GDC ($Gd_{0.1}Ce_{0.9}O_{1-X}$) for low-temperature SOFC electrolytes because it has higher ionic conductivity than YSZ at low temperature. However, open circuit voltage with using GDC ($Gd_{0.1}Ce_{0.9}O_{1-X}$) electrolyte in SOFCs, becomes lower than using YSZ (8 mol% Yttria stabilized Zirconia) electrolyte because GDC has electronic conductivity. In this work, the effect of changing GDC electrolyte thickness on the open circuit voltage has been investigated. Ni-GDC anode-supported unit cells were fabricated as follows. Mixed NiO-GDC powders were pressed and pre-sintered at $1200^{circ}C$. And then, GDC electrolyte material was dip-coated on the anode and sintered at $1400^{circ}C$. Finally the LSCF-GDC cathode material was screen-printed on the electrolyte and sintered at $1000^{circ}C$. Electrolyte thickness was controlled by the number of dip-coating times. Open circuit voltage was measured depending on electrolyte thickness at $650^{circ}C$ and found that the thicker GDC electrolyte was, the better OCV was.