Disclosed is a method for manufacturing a photovoltaic device that includes: providing a substrate having a first electrode formed thereon; forming a first unit cell, the first unit cell including a first conductive silicon layer, an intrinsic silicon layer and a second conductive silicon layer, which are sequentially stacked from the first electrode; exposing to the air either a portion of an intermediate reflector formed on the first unit cell or the second conductive silicon layer of the first unit cell; forming the rest of the intermediate reflector or the entire intermediate reflector on the second conductive silicon layer of the first unit cell in a second manufacturing system; and forming a second unit cell on the intermediate reflector in the second manufacturing system, the second unit cell including a first conductive silicon layer, an intrinsic silicon layer and a second conductive silicon layer, sequentially stacked.