Disclosed herein are a polymer solar cell, comprising a substrate, a first electrode, a hole injection layer, a photoactive layer, and a second electrode, characterized in that an electron-accepting layer is formed between the photoactive layer and the second electrode, and a method of manufacturing the polymer solar cell. The polymer solar cell comprises an electron-accepting layer between the photoactive layer and the second electrode, thereby assuring excellent power conversion efficiency. Furthermore, high power conversion efficiency can also be attained in a low-temperature thermal annealing process.