An organic light emitting device having light emitting units on a substrate is provided. Each light emitting unit includes a first electrode layer, an organic light emitting layer, a second electrode layer, a power line, a resistor line, an insulating layer. The first electrode layer is disposed on the substrate. The organic light emitting layer is disposed on the first electrode layer. The second electrode layer is disposed on the organic light emitting layer. The power line is disposed on the substrate. The resistor line is electrically connected to the first electrode layer, wherein the resistor line partially overlaps with the power line, and an overlapping area occupies 60˜100% of a total area of the resistor line. The insulating layer is disposed between the power line and the resistor line, and a contact hole is disposed in the insulating layer to electrically connect the power line and the resistor line.