Ca3NbGa3Si2O14 (CNGS) single crystals were grown by the micro-pulling-down (μ-PD) method under various atmosphere, Air, Ar + 3%O2 and Ar 100%, and the effects of growth atmosphere on crystal growth and optical properties were investigated. While the CNGS crystal grown in Air indicated orange color, the crystal grown in Ar was colorless. CNGS crystal grown in Air indicated several large absorption peaks around 360 and 500 nm in the transmittance spectrum. In contrast, the crystal grown in Ar didn't indicate these absorption peaks.