Ca-Ru-O compounds were prepared by spark plasma sintering (SPS) using CaCO3 and RuO2 powders at various molar ratio of Ru to Ca (RRu/Ca). CaRuO3 in a single phase was obtained at RRu/Ca = 1.0. A non-stoichiometric solid solution range of CaRuO3 was identified at RRu/Ca = 0.7 to 1.0. The electrical conductivity (σ) showed metallic conduction behavior and increased with increasing RRu/Ca. The electrical conductivity at RRu/Ca = 0.8 to 1.0 increased with decreasing oxygen partial pressure (PO2) and the PO2 dependence of σ became significant with increasing temperature.