A bottle body container made of synthetic resin and including a barrel having left- and right-hand side surfaces symmetrical with respect to the center axis of the container, characterized in that in each of the left- and right-hand side surfaces, regions (7, 8) including the middle region of the barrel are formed with strain-offsetting recesses (9, 10) accommodating changes in the internal pressure of the container, the recesses (9, 10) in the left- and right-hand side surfaces being similar in figure and having the same size, each of the recesses (9, 10) including an upper edge (14), a lower edge (15) and a bottom surface (13), the bottom surface (13) being substantially a gently concave surface at least either in the direction of the generating line of the peripheral wall or in the peripheral direction, each of the recesses being formed at its upper and lower portions with reinforcements (22, 23) for convex surfaces, the reinforcements (22, 23) having a width gradually decreasing from the upper and lower edges of the recess toward the bottom surface, whereby the reinforcements have a substantially triangular frontage shape. The above arrangement allows the fingers and palm of one hand to hold the container at substantially the middle of its barrel from the front or rear side, whereby the container, despite its large capacity and heavy weight, can be safely and firmly held.