The emissive properties of Al2O3/Er3Al5O12 eutectic composite were measured in the temperature range of 1000 to 1700 K. It was confirmed that the Al2O3/Er3Al5O12 eutectic composite has selective emission bands at a wavelength of 1.5 µm attributable to Er3+ ions. It is found that the intensity obeys the T4-law. The emittance of over 0.8 is observed in the selective region. Since these emission bands match up the sensitive region of the GaSb PV cell spectrally, the Al2O3/Er3Al5O12 eutectic composite is a suitable emitter material for using in thermophotovoltaic generation systems. The effects of temperature and thickness on the selective emission efficiency have been studied and discussed.