A thin film transistor substrate of horizontal electric field type includes: a gate line and a first common line formed on a substrate to be in parallel to each other; a data line crossing the gate line and the first common line with a gate insulating film therebetween to define a pixel area; a second common line crossing the first common line having the gate insulating film therebetween; a thin film transistor connected to the gate line and the data line; a common electrode extending from the second common line in said pixel area; a pixel electrode that is parallel to the common electrode and the second common line; a protective film for covering the thin film transistor; a gate pad having a lower gate pad electrode connected to an upper gate pad electrode through a first contact hole; a common pad having a lower common pad electrode connected to an upper common pad electrode through a second contact hole; and a data pad having a lower data pad electrode connected to an upper data pad electrode provided within a third contact hole.