Pinhole generated in the vicinity of a latch protrusion constituting an undercut lock is inspected surely. A main means for solving the above-mentioned technological problem comprises a bottle body which is a biaxial stretching blow molding of synthetic resin having a recess formed in the rear of the body portion, and a handle having an upper lock arm and a lower lock arm extending forward from the upper end and the lower end of an elongated planar grip portion. A rib or a groove is formed to extend rearward in the upper surface of the upper lock arm or in the lower surface of the lower lock arm from the proximity of the rear proximal end of the latch protrusion on at least one of the upper lock arm and the lower lock arm provided with the latch protrusion. An interconnection path for air vent is formed along that rib or groove.
