A collapsible container is provided which can be folded extremely simply and in which a bottom board portion and/or side board portions are not bent easily in use. The collapsible container includes a bottom board portion constituted by one flat sheet board portion. A pair of first side board portions are connected to the bottom board portion so as to extend in a first direction and so as to be opposite to each other. A pair of second side board portions are connected to the bottom board portion so as to extend in a direction perpendicular to the first direction and so as to be opposite to each other. The collapsible container also includes a folding mechanism which may include creases formed on each of the pair of first side board portions so as to extend from a substantially center portion of an upper side of the first side board portion to opposite ends of a lower side of the first side board portion on the bottom board portion side. The collapsible container preferably also includes a pair of side board reinforcing portions. Each of the side board reinforcing portions is provided so as to be connected to the center portion of the upper side of each of the first side board portions between two points where the creases intersect the upper side so that the side board reinforcing portion can be folded to the inside of the first side board portion and can be fitted between the second side board portions.
