Provided are a bulk heterojunction solar cell, including: a substrate; a rear electrode formed on a top surface of the substrate; a core layer comprising a copper indium gallium diselenide (CIGS) layer in which a CIGS powder is formed on a top surface of the rear electrode to be porous, an n-type buffer layer coated on the CIGS powder, and an n-type ZnO layer coated on the n-type buffer layer; and a grid electrode formed on a top surface of the core layer, and a method of manufacturing the same. A porous p-type semiconductor layer is formed by sintering CIGS powders, and then, the n-type semiconductor is coated on the surface of the CIGS powders by using a wet method such that a much larger junction area than a physical size of the solar cell is formed and a power output of the solar cell can be greatly increased.