We newly proposed transparent conductive oxide with diffraction grating structure as an excitation field of surface plasmon resonance working at near-infrared spectral region. We experimentally demonstrated the excitation of SPR using Sn-doped In2O3 films with micro-meter pitched diffraction grating. In this study, we considered the correlation between the grating pitch and the optical reflection spectra. Reflection spectra showed clear polarization properties in infrared spectral region, and the reflection edge has also correlation with the pitch of grating. From these results, the excitation of SPR grating was successfully demonstrated and the wavelength can be tuned by changing the grating pitch in infrared region.