An apparatus for mounting a spout on a plastic film fed longitudinally thereof and intermittently, the apparatus comprising: a punch blade and a punch receiver disposed on opposite sides of the plastic film and opposed to each other in a direction normal to the plastic film, the punch blade and the punch receiver being carried by a carriage; a seal head and a seal receiver disposed on the opposite sides of the plastic film and opposed to each other in the direction normal to the plastic film, the seal head and the seal receiver being spaced from the punch blade and the punch receiver in a direction parallel to the plastic film, the seal head and the seal receiver being carried by the carriage; a punch blade drive by which the punch blade is moved toward the plastic film and the punch receiver when the plastic film is stopped temporarily whenever being fed intermittently so that the plastic film is sandwiched between the punch blade and the punch receiver to be punched by the punch blade, an aperture being formed in the plastic film; a carriage drive by which the carriage is moved for a distance corresponding to a space between the punch blade and the seal head and between the punch receiver and the seal receiver so that the seal head and the seal receiver are disposed at a position at which the punch blade and the punch receiver have been disposed; a spout inserting device by which a spout is inserted into the aperture; and a seal head drive by which the seal head is moved toward the spout, the plastic film and the seal receiver after the spout is inserted so that the spout and the plastic film are sandwiched between the seal head and the seal receiver to be sealed with each other by the seal head, the apparatus making the aperture formed, making the spout inserted and making the spout and the plastic film sealed, respectively at the position. a punch blade and a punch receiver disposed on opposite sides of the plastic film and opposed to each other in a direction normal to the plastic film, the punch blade and the punch receiver being carried by a carriage; a seal head and a seal receiver disposed on the opposite sides of the plastic film and opposed to each other in the direction normal to the plastic film, the seal head and the seal receiver being spaced from the punch blade and the punch receiver in a direction parallel to the plastic film, the seal head and the seal receiver being carried by the carriage; a punch blade drive by which the punch blade is moved toward the plastic film and the punch receiver when the plastic film is stopped temporarily whenever being fed intermittently so that the plastic film is sandwiched between the punch blade and the punch receiver to be punched by the punch blade, an aperture being formed in the plastic film; a carriage drive by which the carriage is moved for a distance corresponding to a space between the punch blade and the seal head and between the punch receiver and the seal receiver so that the seal head and the seal receiver are disposed at a position at which the punch blade and the punch receiver have been disposed; a spout inserting device by which a spout is inserted into the aperture; and a seal head drive by which the seal head is moved toward the spout, the plastic film and the seal receiver after the spout is inserted so that the spout and the plastic film are sandwiched between the seal head and the seal receiver to be sealed with each other by the seal head, the apparatus making the aperture formed, making the spout inserted and making the spout and the plastic film sealed, respectively at the position.