A back film comprises a back film body and a plurality of extension ropes fixed around the back film body to stretch the back film body so that it can be smoothly applied to the user's body. In addition, a dorsal membrane group is also disclosed here. The dorsal membrane group comprises a main dorsal membrane and a plurality of shoulder dorsal membranes.一種背膜，包含有一背膜本體，以及複數個伸展繩固定於背膜本體的周圍，以用來拉伸背膜本體，使其平順地敷貼於使用者的身體。此外，一種背膜組，亦在此揭露。此背膜組包含有一主背膜以及複數個肩背膜。
