The carbothermic reduction of titanomagnetite (TTM) was investigated from a kinetic viewpoint in the temperature range of 1000 to 1150°C employing thermogravimetric analysis (TGA) and quadruple mass spectrometry (QMS). The method of evaluating the fractional reduction in the carbothermic reduction of TTM by TGA was validated. The carbon in char consumed for the reduction of TTM was fully gasified into CO and CO₂, which indicates that the TGA can be coupled to QMS from the viewpoint of mass balance of carbon. The carbon gasification reaction was activated when the Fe₃O₄ in TTM, wustite and Fe coexist at the fractional reduction of 0.21, indicating that Fe-catalyzed nature of Fe was confirmed for the carbon gasification. The activation energy for the reduction in TTM to wustite was evaluated to be 241 kJ/mol and the initial reduction stage is believed to be limited by carbon gasification. In the current study, it was considered that the changeover in reaction mechanism might be carried out from carbon gasification to the reduction in wustite to Fe by CO during the isothermal reduction of TTM with char.