To improve sealing property between a cap and the top end surface of a cylindrical portion of a mouth of a bottle body by making up for an insufficient smoothness of the top surface of an inversion flange which tends to occur caused by blow molding.

There are provided an outer layer 2 made of synthetic resin which constitutes an outer shell having a fixed shape and an inner layer 3 made of flexible synthetic resin which is superposed on the outer layer 2 so as to be peeled off and forms an inner bag, and the layer 3 is bent over a cylindrical part 4, onto which a cap 8 is screwed, from the inside toward the outside and the outer diameter of the layer 3 is formed so as not to hinder the cap 8 from being screwed onto the part 4, and an inversion flange 5, on which the layer 3 is placed, is integrally formed and a ring-shaped packing 10 is fixed to the top surface of the flange 5 by ultrasonic bonding.