Disclosed is an organic light emitting device comprising an anode; a cathode; and a plurality of stacks formed between the anode and the cathode. The plurality of stacks respectively emit their respective light of colors different from one another, wherein the plurality of stacks include a stack emitting blue light and a stack emitting mixed light of blue light and yellow-green to red light. Because the organic light emitting device includes a stack emitting blue light and a stack emitting mixed light of yellow-green to red light and blue light, blue light having a relatively low efficiency may be emitted from the two stacks, whereby overall light emitting efficiency is improved.