The electrochemical deposition process of apatite was monitored in real-time using an electrochemical quartz crystal microbalance (EQCM). A piezoelectric quartz oscillator with titanium was fixed to a cell and connected to a frequency counter. The electrolyte temperature was maintained at 20, 37, and 60 degrees C and the direct current density was constant at 0.2, 0.5, 1.0, and 2.0 mA/cm2. The deposited amount derived from the frequency change increased as electrolyte temperature and current density increased. The critical times, which are the starting times of quick increases of deposition, decreased with them. The critical times observed in the present study, namely in situ, were much shorter than those obtained from real weight change reported in our previous report. The apparent activation energies of the electrochemical deposition of apatite under 1.0 and 2.0 mA/cm2 were about 36.1 and 31.9 kJ/mol, respectively. These results indicate that electro current loading may reduce the activation energy required for the deposition of calcium phosphates.