A slot die coater planarizing an upper surface of an encapsulation layer and a coating method using the same. The slot die coater includes a slit nozzle configured to supply a coating solution. The slit nozzle includes a hole vertically penetrating a center portion thereof, a first bottom surface disposed at a movement direction side of the slit nozzle with reference to the hole, and a second bottom surface disposed at an opposite direction side of the movement direction of the slit nozzle with reference to the hole. A width of the first bottom surface is different from the width of the second bottom surface.