Abstract: Cushion members for a back support are provided on various articles such as a rucksack and a chair to better ventilate between a user's back and the back support, so that the perspiration and heat generation by the user can considerably be reduced. The cushion member for a back support includes a base made from hard plastic material; and a plurality of cushioning elements provided on one side of the base where the user's back contacts, wherein each of the cushioning elements includes a plurality of ribs forming an internal space therein and a plurality of holes formed by the neighboring ribs and communicated with the internal space.