Disclosed is an organic solar cell having a prolonged service life. The organic solar cell comprises: a first electrode which collects holes; a second electrode which collects electrons; a mixed layer which is intercalated between the first electrode and the second electrode and is composed of an electron-donating semiconductor and an electron-attracting semiconductor; and a first electron transport layer and a second electron transport layer both of which are intercalated between the mixed layer and the second electrode. In the organic solar cell, the adhesion between the mixed layer and the second electrode at the interface therebetween can be improved. Therefore, the accumulation of electrical charges produced upon the absorption of light in the mixed layer for the purpose of generating electrical power can be prevented and the electrical charges can be transported to the second electrode with high efficiency, resulting in the prolongation of the service life of the organic solar cell.