A thin film deposition apparatus including a deposition source having a crucible to contain a deposition material and a heater to heat and vaporize the deposition material; a nozzle unit disposed at a side of the deposition source along a first direction and having a plurality of nozzle slits to discharge the deposition material that was vaporized; a plurality of emission coefficient increasing units disposed toward the nozzle unit within the deposition source and increasing a quantity of motion of the deposition material that is discharged toward the nozzle unit; a patterning slit sheet disposed opposite to the nozzle unit and having a plurality of patterning slits arranged along the first direction; and a barrier plate assembly disposed between the nozzle unit and the patterning slit sheet along the first direction, and having a plurality of barrier plates that partition a space between the nozzle unit and the patterning slit sheet into a plurality of sub-deposition spaces.