An LCD (liquid crystal display device) and a manufacturing method thereof are provided. The LCD includes a top substrate, a bottom substrate, and an alignment mark for aligning a polarizing plate on the top substrate or the bottom substrate. Also, the method includes: forming a metal layer on a substrate and forming a gate electrode, a gate line, and an alignment mark; forming a thin film transistor and a data line on the substrate with the gate electrode, the gate line, and the alignment mark; and forming a passivation layer and a pixel electrode on the substrate with a source/drain electrode.