To provide a container the volume of which can easily be reduced into the approximate shape of an n-angled regular prism.

The volume-reducible container 10 has a substantially cylindrical body 14. Easy-to-bend parts 20, 22, and 24 are formed on the body. They are formed along horizontal reference lines 34 and two kinds of oblique reference lines 36 and 38, which are defined on the surface of the body. The easy-to-bend parts are so formed as not to cross one another. The easy-to-bend parts converge at both ends but do not cross one another. Therefore, the propagation of bend is stopped at the non-cross areas. This enables the easy-to-bend parts along the horizontal reference lines to bend inside whereas the easy-to-bend parts along the oblique reference lines to bend outside. As a result, the container is pressed shorter into the approximate shape of an n-angular regular prism. Accordingly, the volume of the container is reduced.