We have proposed micro lens to improve the luminance of red Organic Light Emitting Device. Micro-lenses were applied on the Glass/ITO/ROLED. Size, height and distance of micro-lenses were calculated by FDTD(Finite-Difference Time-Domain) solution. We have simulation result according to micro-lens size (5um, 10um). Result, size of micro lenses were 5 ㎛. Height and distance of micro-lens were all 1 um. The material of micro lenses used silicon dioxide. Result, The highest luminance of OLED which applied with micro-lens was 11,185 cd/m2, when approval voltage was 14.5 V, The device efficiency applying micro-lens increased 3 times than the device which does not apply micro-lens.