Fully dense and infrared transparent YIG (Y3Fe5O12) ceramics was successfully produced by solid-state reaction of Y2O3 and Fe2O3 powders. Its relative density reached 99.8% (5.16g/cm(3)) after sintered at 1400 degrees C for 3hours, and almost 100% relative density (5.17g/cm(3)) was obtained by additional HIP treatment. It was transparent at wavelength ranges longer than 1100nm, and its in-line transmittance (ca. 75%-77%) was very comparable to that of commercial YIG single crystal especially over 1700nm. Faraday rotation angle at 1300 and 1550nm was 224 and 175deg/cm, respectively, and extinction ratio was 35dB and insertion loss polarized at 45 degrees was 0.3dB at 1550nm. It was confirmed that the Faraday effect of polycrystalline material which has numerous grain boundaries and randomized crystal orientations is analogous to that of the single crystal. To the best of our knowledge, this is the first report to achieve highly transparent polycrystalline iron garnet ceramics successfully, and it is expected to use as an optical isolator in optical communication and medical field.