A method for subjecting an elongated substrate to vacuum film formation, comprising the steps of: a) 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; b) degassing the substrate fed in the first direction; c) forming, in a second film formation chamber, a second material film on the first surface of the degassed substrate; d) taking up, in the second roll chamber, the substrate in a roll form, the substrate having the second material film formed thereon; e) unrolling and feeding the substrate taken up in the second roll chamber from the second roll chamber in a second direction from the second roll chamber toward the first roll chamber; f) forming, in a first film formation chamber, a first material film on the second material film formed on the first surface of the substrate fed in the second direction; g) taking up, in the first roll chamber, the substrate in a roll form, the substrate having the first material film laminated on the second material film on the first surface thereof; h) resetting the roll in the first roll chamber, unrolling and feeding the substrate taken up in the first roll chamber from the first roll chamber in the first direction, using a second surface opposite the first surface as a surface for film formation; i) degassing the substrate fed in the first direction; j) forming, in the second film formation chamber, the second material film on the second surface of the degassed substrate; k) taking up, in the second roll chamber, the substrate in a roll form, the substrate having the second material film formed thereon; l) unrolling and feeding the substrate taken up in the second roll chamber from the second roll chamber in the second direction; m) forming, in the first film formation chamber, the first material film on the second material film formed on the second surface of the substrate fed in the second direction; and n) taking up, in the first roll chamber, the substrate in a roll form, the substrate having the first material film laminated on the second material film on each of the first and second surfaces thereof. a) 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; b) degassing the substrate fed in the first direction; c) forming, in a second film formation chamber, a second material film on the first surface of the degassed substrate; d) taking up, in the second roll chamber, the substrate in a roll form, the substrate having the second material film formed thereon; e) unrolling and feeding the substrate taken up in the second roll chamber from the second roll chamber in a second direction from the second roll chamber toward the first roll chamber; f) forming, in a first film formation chamber, a first material film on the second material film formed on the first surface of the substrate fed in the second direction; g) taking up, in the first roll chamber, the substrate in a roll form, the substrate having the first material film laminated on the second material film on the first surface thereof; h) resetting the roll in the first roll chamber, unrolling and feeding the substrate taken up in the first roll chamber from the first roll chamber in the first direction, using a second surface opposite the first surface as a surface for film formation; i) degassing the substrate fed in the first direction; j) forming, in the second film formation chamber, the second material film on the second surface of the degassed substrate; k) taking up, in the second roll chamber, the substrate in a roll form, the substrate having the second material film formed thereon; l) unrolling and feeding the substrate taken up in the second roll chamber from the second roll chamber in the second direction; m) forming, in the first film formation chamber, the first material film on the second material film formed on the second surface of the substrate fed in the second direction; and n) taking up, in the first roll chamber, the substrate in a roll form, the substrate having the first material film laminated on the second material film on each of the first and second surfaces thereof.