A method of manufacturing an organic light emitting display device includes: providing a capacitor on a substrate; providing a protection layer on the capacitor; providing an organic light emitting diode on the protection layer; and providing an encapsulation layer which encapsulates the organic light emitting diode. The providing the capacitor includes: providing a bottom electrode including an oxide semiconductor, on the substrate; providing an insulation layer on the substrate and overlapping the bottom electrode; annealing the bottom electrode to increase a carrier density of the bottom electrode; and providing an intermediate electrode on the insulation layer and overlapping the bottom electrode.