A fabricating method of an array substrate for an in-plane switching liquid crystal display device includes: forming a gate line and a common line on a substrate, the common line spaced apart from the gate line; forming a data line crossing the gate line to define a pixel region; forming a thin film transistor connected to the gate line and the data line; forming a pixel electrode and a common electrode in the pixel region, each of the pixel electrode and the common electrode including an opaque metal layer; and irradiating ultraviolet rays onto the opaque metal layer to form a metal oxide layer on the opaque metal layer.