In this paper, the effect of electric current on sintering of hydroxyapatite (HAp) in spark plasma sintering (SPS) process was investigated. The carbonate partially substituting hydroxyapatite was sintered up to 900 °C, and CO2 evolved from HAp powder were measured in situ by using mass spectroscopy apparatus in the same time. The same gas analysis was performed in thermal analysis as comparison. In the thermal analysis, CO2 gas was evolved at about 600 °C. On the other hand, in the SPS process, CO2 gas was detected at lower temperature than that of thermal analysis. This result indicates that the surface of hydroxyapatite particles would be heated up locally in SPS process due to electric current.