A straight-split pouch, a method for manufacturing the pouch, and a device for manufacturing the pouch. The pouch is based on a front synthetic resin sheet and a rear synthetic resin sheet, has a notch marking the tear starting point at the openable portion, and has a series of multiple grooves for splitting disposed at a predetermined distance from one another along a straight line at the openable portion starting from the notch. The method includes producing a base film; producing the grooves for splitting; applying an adhesive to the surface protection layer and drying the layer; adhering the base film to the surface protection layer; sealing a large-area sheet; and cutting the sealed large-area sheet and forming the notch. The device includes first and second winding portions; an adhesive application portion; a chamber; a shaping apparatus; a laminating treatment portion; and a heat seal and cutting portion.