The present invention provides oxygen partial pressure control apparatuses that can control the partial pressure of oxygen in atmospheric gases in processing apparatuses or the like to within the range of 0.2 to 10−30 atm, while maintaining low material and operational cost conditions. The present invention provides oxygen partial pressure control apparatuses in which air or pure oxygen is supplied to the inside of a heating furnace that can heat and maintain solid electrolytes at an operational temperature, wherein the heating furnace houses at least one oxygen pump comprising a solid electrolyte with a tubular structure and at least two oxygen sensors comprising a solid electrolyte with a tubular structure, wherein the at least one oxygen pump described above and the at least two oxygen sensors described above are placed in parallel such that the aforementioned air or pure oxygen serves as a purge gas that sweeps the surroundings of each solid electrolyte tube, and wherein they are connected such that a common process gas can flow through each solid electrolyte tube.