Disclosed herein is a method of forming a light-absorbing layer of a polycrystalline silicon solar cell, including: forming a polycrystalline silicon layer on a back electrode; forming an intrinsic amorphous silicon layer on the polycrystalline silicon layer; and heat-treating the transparent insulating substrate to vertically crystallize the intrinsic amorphous silicon layer using the polycrystalline silicon layer as a seed for crystallization through a metal induced vertical crystallization (MIVC) process to form the intrinsic amorphous silicon layer into a light-absorbing layer made of polycrystalline silicon, and is a method of fabricating a high-efficiency polycrystalline silicon solar cell using the light-absorbing layer.