To provide a composite article set such as a letter set, which suppresses the free shift of an envelope in an outer bag, without the use of a dedicated member.

This composite article set comprises: a letter paper 2; the envelope 3; a leaflet 5 on which predetermined characters etc. are printed; and the outer bag 6 with a storage space 61s in which the letter paper 2, the envelope 3 and the leaflet 5 can be housed. The leaflet 5 is provided with an envelope holding means X for regulating the free shift of the envelope 3 in the storage space 61s.