A method of manufacturing an organic light emitting diode (OLED) display device includes: providing a substrate including a display area and a non-display area; forming an organic light emitting diode element in the display area; forming a barrier wall around the display area and spaced apart from the organic light emitting diode element; performing a plasma treatment on the substrate on which the organic light emitting diode element is formed; and forming a thin film encapsulation layer for coating the organic light emitting diode element, wherein forming the thin film encapsulation layer includes: forming at least one inorganic layer; and forming at least one organic layer inwardly of the barrier wall.