Disclosed is a method for fabricating a thin film transistor for a liquid crystal display device using four masks and without using a diffraction mask. The method of the present invention uses a first mask when forming a gate electrode, a second mask when forming an active pattern, a third mask when forming a plurality of contact holes at an upper portion of a channel layer, and a fourth mask when forming a pixel electrode and source and drain electrodes, so that the resulting liquid crystal display device may be completed by four masks without using a diffraction exposure method. Instead of using a diffraction mask, the present invention uses different etching rates between an insulating layer and an electrode layer, which is used for source and drain electrodes, in fabricating a thin film transistor.