Disclosed is a method for manufacturing a photovoltaic device. The method comprising: forming a first electrode on a substrate; forming a first unit cell comprising an intrinsic semiconductor layer on the first electrode; forming an intermediate reflector on the first unit cell, and the intermediate reflector comprising a plurality of sub-layers stacked alternately by changing a flow rate of non-silicon based source gas; forming a second unit cell comprising an intrinsic semiconductor layer on the intermediate reflector; and forming a second electrode on the second unit cell.