The film formation method comprises the steps of: unrolling and feeding an elongated substrate wound in a roll form from a first roll chamber in a first direction from the first roll chamber toward a second roll chamber, using a first surface as a surface for film formation; degassing the substrate fed in the first direction; forming a second material film on the first surface of the substrate in a second film formation chamber; taking up the substrate in a roll form in the second roll chamber, the substrate having the second material film formed thereon; unrolling and feeding the substrate from the second roll chamber in a second direction from the second roll chamber toward the first roll chamber; forming a first material film on the second material film in a first film formation chamber; taking up the substrate in a roll form in the first roll chamber.