A manufacturing method of a light emitting device is provided. A first electrode is formed on a substrate. The first electrode includes a patterned conductive layer, and the patterned conductive layer includes an alloy containing a first metal and a second metal. An annealing process is performed on the first electrode, so as to form a passivation layer at least on a side surface of the first electrode. The passivation layer includes a compound of the second metal. A light emitting layer is formed on the first electrode. A second electrode is formed on the light emitting layer.