A method and device for supplying spout attachment bags, in which one vertical plane is set as a reference plane N, and the center line (C) of a corner-spout attachment bag (2) positioned at the distal end of a conveyor magazine (7) is located in the reference plane N. A suction cup (28) picks up the bag and is rotated by a specific angle (θ) centered on a vertical rotational axis (O) when being transferred. When the suction cup picks up the positioned bag, the rotational axis is set to a position where a corner opening vertical line (M) that passes through the center of a corner opening (3) of the bag intersects the reference plane N. The bag held by the suction cup is sent to a positioning conveyor and positioned by stoppers (52, 53) with the corner opening vertical line being in the reference plane.