Optical properties of Ga0.82In0.18N p-n homojunction light-emitting-diode are investigated by the photovoltaic, photoluminescence-excitation, electroluminescence (EL), and photoluminescence (PL) measurements. Although the X-ray diffraction measurements indicate a uniform InN molar fraction x in the sequentially grown n-and p-type Ga0.82In0.18N layers, the EL and PL exhibited different peak energies at room temperature. The difference is explained by the emission models in the n-and p-type of Ga0.82In0.18N layers. The results demonstrate a potential use of Ga1-xInxN p-n homojunction for further development of functional device structures.