This bottle (1) has a cylindrical shape with a bottom and is formed from a synthetic resin material. The bottom wall (19) of the bottom is provided with: a ground-contact section (18) positioned at the outer peripheral edge; a rising peripheral wall (21) that extends upwards and that connects to the ground-contact section (18) from the inside in the direction of the bottle diameter; a mobile wall (22) that protrudes inwards in the direction of the bottle diameter from the upper end of the rising peripheral wall (21); and a recessed peripheral wall (23) that extends upwards from the inner end of the mobile wall (22) in the direction of the bottle diameter. Also, the mobile wall (22) is disposed movably together with the recessed peripheral wall (23) in the upward direction centered on the section (25) of connection with the rising peripheral wall (21). Also, a plurality of ribs (26) are provided radially to the mobile wall (22) centered on the bottle axis (O).
