Score lines are formed on package material. A spout attachment hole is formed in a portion corresponding to a top gusset section of a pouch. A spout is attached to the spout attachment hole. A portion corresponding to a peripheral edge of the top gusset section of the pouch and a portion corresponding to a top edge of a body section of the pouch are heat-sealed, and the package material is cut in the width direction. Portions corresponding to side edges of the body section of the pouch are heat-sealed, and a portion corresponding to a peripheral edge of a bottom gusset section and a portion corresponding to a peripheral edge of a bottom end portion of the body section are heat-sealed. The heat-sealed portions formed at the portions corresponding to the side edges of the body section of the pouch are cut so a spouted pouch package is released.