We have investigated Fe and Ni codoping effect into SnO 2. Room-temperature diluted ferromagnetic semiconductors with the enhancement of magnetization can be prepared in case of codoping. The saturation magnetization can be controlled by means of the Fe and Ni codoping ratios. The electronic structures were investigated by x-ray absorption spectroscopy (XAS) and Mössbauer spectrometry. Fe 3 states were revealed by the isomer shift values. XAS revealed Ni 2+ states, which suggests that the double-exchange-like ferromagnetic interaction between the diluted magnetic ions mediated by oxygen vacancies becomes a possible origin of room-temperature ferromagnetism.