To impart rigidity to the whole bottle body, and prevent a deforming panel part from recessing by a gripping force even when the deforming panel part is gripped by hand by providing a deforming panel for which a plurality of valley-shaped deforming parts being constituted of tilted walls which tilt inward, are arranged, and a thin recessed groove is formed around the valley-shaped deforming parts.

On a wall surface 2 of the body part of a square bottle main body b1 made of a plastic, a plurality of valley-shaped deforming parts 31 being constituted of a tilted wall 311 which tilt inward from the wall surface 2 of the body par, are arranged, and at the same time, a thin recessed groove 32 is formed to surround the valley-shaped deforming part 31 to form a deforming panel part 3, and the deforming panel part 3 is provided on the wall surface 2 of the body part. By doing so, a deformation of the bottle main body due to a pressure being generated in the bottle, is absorbed by a deformation of the deforming panel part 3, and at the same time, the rigidity of the bottle is strengthened by the wall surface of the body part between two valley-shaped deforming parts 31, as a lateral bridge 21, and for this reason, even when the deforming part of the bottle is gripped by hand, the spot is prevented from recessing by the gripping force.