An organic electroluminescent device with an encapsulation film formed by wet processing and a manufacturing method thereof. The organic electroluminescent device includes a laminate structure including an anode, an organic light emitting layer and a cathode sequentially disposed on a substrate, and an encapsulation film having a polymer layer made of a polymerization product of a vinyl monomer covering the laminate structure. In the method for manufacturing the organic electroluminescent device, a laminate structure including an anode, an organic light emitting layer and a cathode sequentially disposed is formed on a substrate. An organic solution containing a vinyl monomer and a polymerization initiator is coated on the laminate structure. A polymerization reaction is induced to the organic solution coated on the laminate structure, thereby forming an encapsulation film made of a polymer layer on the laminate structure.