The invention discloses an apparatus for supplying spout attachment bags. A positioning apparatus (12) is configured such that even when the rear end (a spout attachement opening (2)) of a spout attachment bag that is positioned by a side edge block (610 and an upper edge block (62) offsets from a reference position (P0), and when the spout attachment bag is supplied to a spout attachment apparatus (75), the height of spout attachment opening of the spout attachment bag is always constant. The position of the spout attachment opening of the spout attachment bag that is positioned in the positioning apparatus is detected, the detected position of the spout attachment opening is compared with the preset reference position, a servo motor (68) is controlled to action on the basis of the offset of the two positions, the position of a swinging end of an arm (66) which swings upwardly is corrected, the height position of the spout attachment opening of the spout attachment bag which is changed into a vertical posture is kept constant.