To provide a foldable envelope which can be seen reasonably, for example, in a train by opening the envelope like a book.

This foldable envelope 10 is formed by folding a sheet of a printed matter 11 into a rolled letter paper-like shape. When a sheet of the printed matter 11 is folded into the envelope 10, the end edge 12a folded outside is releasably stuck, and the upper edge 10c and the lower edge 10d of the envelope 10 are releasably stuck, and the folded part 10a overlapped on one side of the envelope 10 is stuck, and a perforation 15 is formed in the folded part 10d overlapped on the other side of the envelope 10.