In this paper, the effect of doping of Manganese on to Cerium oxide for thermochemical two-step water splitting cycle for produce the hydrogen was experimentally studied. In order to compare the oxygen/hydrogen productivity, pure CeO2, coprecipitation method applied Mn-CeO2, and direct doping calcination method adopted Mn-CeO2 were used to thermo-chemical two-step water splitting cycle tests. The synthesized sample powders were coated on the reticulated porous foam device and tested in the fixed bed type reactor for the temperature of 1400 C for thermal reduction step, and 1200 C for water decomposition step through 5 cyclic tests. The redox reactive foam devices were irradiated by 3kW sun-simulator, and all samples recorded successful oxygen/hydrogen production. Among the 3 sample devices, the 15 mol% Mn-CeO2 foam device which synthesized by direct doping calcination method shows highest hydrogen production amount and H2/O2 conversion ratio. o o