The present invention relates to a flat panel display, and more particularly, to a method of fabricating an organic light emitting display device so as to improve device characteristics by patterning a plurality of organic layers using a heat transfer method to optimize thicknesses according to R, G and B pixels. The method includes: forming lower electrodes of R, G and B pixels on an insulating substrate; forming an organic layer on the insulating substrate; and forming an upper electrode on the organic layer. Formation of the organic layer includes forming a hole injection layer and a hole transport layer of the R, G and B pixels on the entire surface of the substrate as a common layer. The R and G emission layers are patterned by a heat transfer method using a heat transfer device having a transfer layer such that an organic layer is patterned to a thickness obtained by subtracting a thickness of the B emission layer from the thicknesses of the R and G emission layers required in R and G colors.