A method for fabricating a sensor includes: forming, on a base substrate, a pattern of a source electrode and a drain electrode, a pattern of a data line, a pattern of a receiving electrode, a pattern of a photodiode, and a pattern of a transparent electrode disposed by using a first patterning process; forming a pattern of an ohmic layer by using a second patterning process; forming a pattern of an active layer by using a third patterning process; forming a pattern of a gate insulating layer by using a fourth patterning process, wherein the gate insulating layer has a via hole above the transparent electrode; and forming a pattern of a gate electrode, a pattern of a gate line, and a pattern of a bias line connected to the transparent electrode via the via hole above the transparent electrode by using a fifth patterning process.